''Pachypodium'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
succulent
In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...
spine-bearing trees and shrubs, native to Madagascar and Africa. It belongs to the
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
Apocynaceae
Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of the ...
.
Genus characteristics
All ''Pachypodium'' are
succulent
In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...
plants that exhibit, to varying degrees, the morphological
characteristics of
pachycaul trunks and
spinescence. These are the most general features of the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
and can be considered distinguishing characteristics.
The pachycaul trunk is a morphologically enlarged trunk that stores water so as to survive seasonal
drought
A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...
or intermittent periods of root desiccation in exposed, dry, and rocky conditions. Whereas there is great variation in the habit of the plant body, all ''Pachypodium'' exhibit pachycaul growth. Variation in habit can range from dwarf flattened plants to bottle shaped shrubs to dendroid-shaped trees.
The second general characteristic of ''Pachypodium'' is spinescence, or having spines. The spines come clustered in either pairs or triplets with these clusters often arranged in rings or whorls around the trunk. Spines emerge with leaves, and like leaves grow for a short period before stopping growth and hardening. Spines do not regenerate so weathering and abrasion can wear away all but the youngest spines from older specimens - leaving smooth trunks and branches.
To some extent,
branch
A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk (botany), trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term '' ...
es are a characteristic of the genus. Some caution is warranted in over-generalizing this characteristic. ''
Pachypodium namaquanum
''Pachypodium namaquanum'', also known as halfmens or elephants trunk, is a succulent plant of Southern Africa. The genus name ''Pachypodium'' is from the Greek for 'thick foot', an allusion to its swollen base, while the species name ''namaq ...
'' is often branchless. ''
Pachypodium brevicaule
''Pachypodium brevicaule'' is a species of plant that belongs to the family Apocynaceae.
Distribution
This plant is native to Madagascar, from the south of Antananarivo to the Itremo Mountains.
Habit
A flattened, tuberous, cactus-like plant wit ...
'' has no clear branches, and indeed may have evolved an alternative to branching in the form of nodes from which leaves, spines, and
inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...
s emerge. In general ''Pachypodium'' have few
branch
A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk (botany), trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term '' ...
es. Since the environmental stresses and factors that contribute to branching can vary widely even in small areas, individual plants of the same species exhibit wide variation in branching morphology.
Unlike many members of the
Apocynaceae
Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of the ...
, including some members of the superficially similar ''Adenium'', ''Pachypodium'' species do not exude a milky
latex
Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well.
In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...
. Rather, the
sap
Sap is a fluid transported in xylem cells (vessel elements or tracheids) or phloem sieve tube elements of a plant. These cells transport water and nutrients throughout the plant.
Sap is distinct from latex, resin, or cell sap; it is a separ ...
is always clear.
Morphology
The
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
of the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Pachypodium'' varies significantly both within and between species and is highly responsive to its immediate surrounding
microenvironment. ''Pachypodium'' do not overly respond morphologically to larger vegetative zones. For example, ''Pachypodium'' can sometimes occur in prehumid vegetative zones where a taxon might find a suitable habitat on a rocky, sunny
inselberg
An inselberg or monadnock () is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain.
In Southern Africa a similar formation of granite is known as a koppie, a ...
jutting above the humid canopy of the forest.
Morphologically, ''Pachypodium'' can be highly ''flexible'' in organization. Branching, if present at all, can be from either the base of the plant or at the crown. Freeform branching is a morphological adaptation to factors of the immediate microenvironment which, by their diversity, account for the wide range of habits:
* flattened dwarf species less than 8 cm tall but reaching 40 cm in diameter
* bottle- or oval-shaped shrubs to 4 m tall
* both branching and unbranched cigar- and cactus-like trees to 5 m tall.
Despite microenvironmental variation, ''Pachypodium'' are always succulent and always exhibit pachycaul trunks. ''Pachypodium'' are usually spinescent, but individual variation in spinescence as well as weathering and abrasion can result in plants with few if any spines.
Adaptive features
Variation among ''Pachypodium'' species is significant but all ''Pachypodium'' are succulent plants inhabiting seasonally or chronically dry landscapes. The genus employs two morphological
adaptations
In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the ...
to these
xeric
Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (ancient Greek xērós, “dry") shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this h ...
, isolated, habitats: Pachycaul trunks and spinescence.
Pachycaul trunks
''Pachypodium'' trunks and branches are thickened with water-storing tissue. Plants must rely on the food and water stored in their thickened trunks during seasonal or intermittent drought when leaves have been shed and no water is available from the substrate. In addition to the lower surface-to-volume ratio which aides in water retention, the thickened trunks and branches can also possess photosynthetic surface tissue to allow nutrient synthesis even when leaves are not present.
Some species of pachypodium have developed geophytic pachycaul trunks, or trunks that are beneath the
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
's surface. These geophytic trunks are
caudex
A caudex (plural: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly a basal stem structure from which new growth arises.pages 456 and 695
In the strict sense of the term, meaning a stem, "caudex" is m ...
es, enlarged stems or trunks that store water. They should not be mistaken for
root
In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...
s, because the enlargement occurs above the point where the roots branch off the main axis of the trunk.
Spinescence
The various species of Pachypodium are more or less heavily spined. Species from more arid regions have evolved denser and longer spines. Fog condenses on their spines in the form of dew, which drips down to the ground and increases the amount of moisture that's available to their often shallow roots.
The concept of "
micro
Micro may refer to:
Measurement
* micro- (μ), a metric prefix denoting a factor of 10−6
Places
* Micro, North Carolina, town in U.S.
People
* DJ Micro, (born Michael Marsicano) an American trance DJ and producer
*Chii Tomiya (都宮 ちい ...
-
endemism
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
" plays an important role in this relationship between adaptation mechanisms and speciation. It suggests a certain small scale "nativeness" by virtue of originating or occurring naturally in a particular place or
location
In geography, location or place are used to denote a region (point, line, or area) on Earth's surface or elsewhere. The term ''location'' generally implies a higher degree of certainty than ''place'', the latter often indicating an entity with an ...
. The
landscape
A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or man-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes the ...
of Madagascar is a perfect example of "micro-endemism" for species of ''Pachypodium'' and other taxa. Three factors can be seen to attribute speciation, or the occurrence of species diversity, via adaptive mechanisms to accelerated
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
as it occurs within the
xeric
Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (ancient Greek xērós, “dry") shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this h ...
landscape and
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
.
(1) The variation of geology and topology in dry climates is thought to have a greater effect upon plants than in areas with high rainfall. Xeric environments are thus more demanding of adaptive mechanisms to aid in the plant's survival than in places where rainfall is plentiful. The more the demanding, generally the more "mechanized" or "mechanisms" are needed to aid the plants' survival.
(2) The geological formations of locally xeric landscapes break up
populations
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
of
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s, i.e.
plants
Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
, into smaller groups, where each group can initially interbreed but, with time, develop new
genotypes
The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...
and cannot be bred with exception to natural
hybridization. Localized
geology
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...
becomes harder to cross over for a given population to be "continuous" in a xeric geological landscape, because more demands are placed on the population. Therefore, populations are broken down into smaller units within this landscape. Groups of the original population become located to unique
microenvironments within the landscape. Accordingly, measures to adapt to these microenvironments become more singular to the isolated habitat. Adaptive mechanisms are employed so as to aid the survival of the plant group. This adaptation eventually, in part, leads to speciation in the habitat, or diverse species across the spectrum of the landscape.
(3) Taxa tend to develop specialized xeromorphoric structures at some architectural level in
arid
A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ar ...
, geological and
topological
In mathematics, topology (from the Greek words , and ) is concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing ...
landscapes, where a strategy of a "flexible" and "strict" architectural, organizational morphology at various levels of structure for ''Pachypodium'' becomes advantageous to succeeding in the isolated, specialized landscape. This strategy is seen in the manifest ''flexible'' variations of habit in species of ''Pachypodium'' while all the same they are "strictly" xeromorphic pachycaul trunks meant to conserve water for dry periods. At another level of structure, namely that of organs, we can see that
dew
Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation.
As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at wh ...
and
fog
Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Reprint from Fog can be considered a type of low-lying cloud usually resembling stratus, and is heavily influ ...
dripping spines are examples of a xeromorphic adaptive mechanized organ responding to microenvironments.
These newly created species from within the xeromorphic landscape take on different characters as responses to the
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
. For instance, there is an advantage to morphologically developing into bottle-shaped "shrubs" where the plants exist in open, sunny microenvironments on top of porous
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
. Little competition exists for height within the habitat. Likewise, where competition for resources is more competitive—''both in the number of species and the height of surrounding plants''—there are times when it is to the advantage of a plant to develop into arborescent, dendroid “trees.” This development is because these particular ''Pachypodium'' must compete with other plants for resources in a dry deciduous forest, composed of, perhaps, arborescent ''
Aloe
''Aloe'' (; also written ''Aloë'') is a genus containing over 650 species of flowering succulent plants.WFO (2022): Aloe L. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-4000001341. Accessed on: 06 Nov 2022 The most wid ...
'', members of the
Didiereaceae
Didiereaceae is a family of flowering plants found in continental Africa and Madagascar.
It contains 20 species classified in three subfamilies and six genera. Species of the family are succulent plants, growing in sub-arid to arid habitats. Seve ...
genera ''
Alluaudia
''Alluaudia'' is a genus of flowering plants in the family Didiereaceae. There are six species, all endemic to Madagascar.
Most occur in the southwestern subarid forest-thicket vegetation of the island.
Species of ''Alluaudia'' are dioecious, ...
'', ''Alluaudiopsis'', ''Decaryia'', and ''Didierea'' (all endemic to Madagascar), and ''Uncarina'' species, for instance.
The adaptive mechanism in a morphological form and an ecological response to habitats are typically manifested together at once for the genus ''Pachypodium''.
Examining ''Pachypodium'' reveals characteristics of various organs that adapt to the microenvironment. These adaptations, variations on habit,
trunks,
branches
A branch, sometimes called a ramus in botany, is a woody structural member connected to the central trunk of a tree (or sometimes a shrub). Large branches are known as boughs and small branches are known as twigs. The term ''twig'' usually ...
, branchlets,
spines,
leaves
A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
, or
flowers
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
, are plentiful in demonstrating how ''Pachypodium'' as a genus fosters greater variation in its speciation. The manner in which speciation occurs in ''Pachypodium'', therefore, is apparent: adaptive mechanisms on a morphological level respond to the microenvironment of ''Pachypodium'' habitat. The genus' unique organizational, architectural morphology shapes plants that are highly, adaptively responsive to their immediate, surrounding, microenvironments. The duplicity of an adaptive mechanism that is at once "strict" and "flexible" at differing levels of plant physiology, or structure, has granted ''Pachypodium'' the ability to evolve within the landscape into variations that fulfill an
ecological
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
niche as various species.
The
hypothesis
A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...
of micro-endemism, therefore, states that speciation occurs in small specific habitats as aided by adaptive mechanism occurring in geological, topographical, and climatic isolation. Geologically and topographically, plant populations in xeric climates are broken down into smaller groups. The microclimate responds to the given location transforming it into a habitat. Isolated, the duplicity of organization in ''Pachypodium'' form through geology and location significant variation where over evolutionary time a new species might develop, if not have developed. The development of new species is through, in part, the adaptive mechanisms of pachycaul and spinescence as well as strict and flexible structural organization at various levels of plant physiology.
Taxonomy
Number of species
There are now 25 known species, of which 20 come from
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, where isolated
landscape
A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or man-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes the ...
s and
micro
Micro may refer to:
Measurement
* micro- (μ), a metric prefix denoting a factor of 10−6
Places
* Micro, North Carolina, town in U.S.
People
* DJ Micro, (born Michael Marsicano) an American trance DJ and producer
*Chii Tomiya (都宮 ちい ...
-environmental conditions have produced highly
specialized species. The species count continues to grow as ''
Pachypodium menabeum
''Pachypodium'' is a genus of succulent spine-bearing trees and shrubs, native to Madagascar and Africa. It belongs to the family Apocynaceae.
Genus characteristics
All ''Pachypodium'' are succulent plants that exhibit, to varying degrees, the ...
'' has been resurrected from invalid taxonomy and ''
Pachypodium makayense
''Pachypodium'' is a genus of succulent spine-bearing trees and shrubs, native to Madagascar and Africa. It belongs to the family Apocynaceae.
Genus characteristics
All ''Pachypodium'' are succulent plants that exhibit, to varying degrees, the ...
'' added newly to the list. One can speculate that in regions such as
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, there might still be unidentified species that are confined to a single rocky outcrop or an
inselberg
An inselberg or monadnock () is an isolated rock hill, knob, ridge, or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain.
In Southern Africa a similar formation of granite is known as a koppie, a ...
.
Affinities within the Apocynaceae
The family Apocynaceae before it included Asclepiadaceae had 3
genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
that can be considered
succulent
In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meani ...
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s: ''Adenium'', ''Pachypodium'', and ''
Plumeria
''Plumeria'' (), known as frangipani, is a genus of flowering plants in the subfamily Rauvolfioideae, of the family Apocynaceae. Most species are deciduous shrubs or small trees. The species variously are endemic to Mexico, Central America, and ...
''. The first two genera (''Pachypodium'' and ''Adenium'') are generally assumed to have a close association with each other. Studies; however, of these two genera reveal that they are not as intimately close as once thought.
However, a study of key characteristics of the taxon and a
cladistic
Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...
study of the
subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
Apocynoideae and the family
Asclepiadaceae (before its merging with the
Apocynaceae
Apocynaceae (from ''Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison Members of the ...
), demonstrates that this closed association is not warranted. True, both are succulent plants and pachycaul. According to Leeuwenberg however, ''Adenium'' is maintained in the subtribe Neriinae, placed underneath the
tribe
The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English language, English is in the discipline of anthropology. This definition is contested, in p ...
Wrightieae whereas ''Pachypodium'' is placed beside them in the subtribe Pachypodiinae, within the tribe Echiteae. Though related, these taxa means that the two are not intimately related.
Distribution and habitats
Distribution
''Pachypodium'' are native to
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
and continental
Southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...
, i.e.
Angola
, national_anthem = " Angola Avante"()
, image_map =
, map_caption =
, capital = Luanda
, religion =
, religion_year = 2020
, religion_ref =
, coordina ...
,
Zaire
Zaire (, ), officially the Republic of Zaire (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
,
Botswana
Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label=Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kalahar ...
,
Mozambique
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
,
Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
,
South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
,
Eswatini
Eswatini ( ; ss, eSwatini ), officially the Kingdom of Eswatini and formerly named Swaziland ( ; officially renamed in 2018), is a landlocked country in Southern Africa. It is bordered by Mozambique to its northeast and South Africa to its no ...
and
Zimbabwe
Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and Mozam ...
.
Habitat
In elevation, ''Pachypodium'' in both mainland
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
and
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
grow between an altitude of sea level, where some
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
grow in
sand dunes
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...
, such as ''
Pachypodium geayi
''Pachypodium geayi'' is a species of ''Pachypodium'' that originated from Southwest Madagascar. It has a metallic grey pachycaul trunk and the leaves are thin and grey-green, with a bright pink mid-rib. The plant has white flower
A flower, ...
'', to for ''
Pachypodium lealii
''Pachypodium lealii'', the bottle tree, is a species of plant included in the ''genus'' ''Pachypodium''. The scientific name derives from the 19th century Portuguese geologist Fernando da Costa Leal, who described the bottle tree during an exp ...
'' in southern Africa and for ''
Pachypodium brevicaule
''Pachypodium brevicaule'' is a species of plant that belongs to the family Apocynaceae.
Distribution
This plant is native to Madagascar, from the south of Antananarivo to the Itremo Mountains.
Habit
A flattened, tuberous, cactus-like plant wit ...
'' in Madagascar.
In continental southern Africa, the extreme
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
s range from in some locations to as much as . Whereas in Madagascar, with not such a great temperature amplitude, the temperature ranges from .
A generalization about
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
regimes for both southern Africa and Madagascar does not have much meaning because the habitats of ''Pachypodium'' vary so greatly with a moisture regime. In some places, ''Pachypodium'' receive annually from as little as from the southern part of Africa to a high level of . A precipitation regime for a species of ''Pachypodium'', therefore, depends upon a habitat's location relative to the influences of the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
and
Indian
Indian or Indians may refer to:
Peoples South Asia
* Indian people, people of Indian nationality, or people who have an Indian ancestor
** Non-resident Indian, a citizen of India who has temporarily emigrated to another country
* South Asia ...
Oceans and the various mountain ranges of southern continental Africa and of Madagascar.
The genus grows in areas where there are significant periods of
dry months that range from five months to ten months. It would seem likely that the Atlantic and India Oceans pay a major role in the creation of weather conducive to
rainfall
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
, not to mention
mountain
A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited Summit (topography), summit area, and ...
ranges
In the Hebrew Bible and in the Old Testament, the word ranges has two very different meanings.
Leviticus
In Leviticus 11:35, ranges probably means a cooking furnace for two or more pots, as the Hebrew word here is in the dual number; or perhaps ...
. For example, the
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion situated in the western and northern part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agric ...
with their long dry season and severe limestone ridden soils provide one ideal setting for ''pachypodium''.
''Pachypodium'' grows in various types of
substrates. Some species only grow in one substrate whereas other will grow in several. The degree to which a taxon can grow in a given substrate seems to determine how specialized its
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
is within the
landscape
A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or man-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes the ...
and
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
s. On outcrops, steep hills, and inselbergs, the plants are subjected to fluctuating
moisture
Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...
, high
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
s, and
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer.
Thermometers are calibrated in various temperature scales that historically have relied o ...
extremes. Only plants with special adaptations to exposure and extreme drought can survive, let alone thrive, on these exposed geological habitats. ''Pachypodium'' root in cleft,
fissures
A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes.
Ground fissure
...
, and crevices of those rocky formations. The non-succulent roots penetrate deeply into the acuminated
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
,
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
, and
humus
In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...
in these crevices. Moisture is able to seep deep into these crevices. Very little
transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...
occurs. In this manner, rocky substrates provide moisture in the habitat. This saturation of crevices can only occur, however, if there is not a considerable runoff from the rock's surface and if there is abundant fine soil in the cracks that, in turn, retain water. The
substrate, therefore, plays a critical role in the creation of micro-environmental "arid islands."
Sand readily store water because it is taken up easily and there is less evaporation except for the top layer. Very deep sand; however, has the problem of seepage. Yet in moderation shallow and deep sand substrates have water available to ''Pachypodium''. With shallow sand substrates, ''Pachypodium'' grow on sand dunes near the sea. Where water is in deep sandy substrate, ''Pachypodium'' grow on sand "over"
laterite
Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...
red soil. Laterite soil is a largely impermeable soil that traps water for the use of the flora that include ''Pachypodium''.
Protection status
Internationally ''Pachypodium'' are protected under the
CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
treaty. According to it, members of this genus cannot be collected from endemic, native locations within the landscape. They are not easily, readily imported and exported between nations either. The protection afforded by the CITES treaty responses to two issues:
*The esteem the genus has within Collector's and Nursery Trade. As highly esteemed plants, succulent enthusiast desire to collect more and more species and
cultivar
A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...
s. In the case of ''Pachypodium'',
seed
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
, seedlings, and even mature, nursery-grown specimen plants are fortunately available readily in Nursery Trade.
*Destruction of the genus's endemic
habitats
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
, e.g. through
agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...
.
Extinction
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
of identified species seems yet unlikely, as the collection of seed and the cultivation of the plant safeguard the genus.
History of the genus
The early history of the
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Pachypodium'' demonstrates the typical process of a taxon becoming a new genus. Initially debate occurred over if ''Pachypodium'' belonged to the genus ''
Echites'' or if it constituted a separate genus. ''Pachypodium ''were first published as a unique genus, separate from ''Echites'', by
Leandley in 1830.
Then the debate centered on the
nomenclature
Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal naming conventions, conventions of everyday speech to the i ...
of
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
uniquely found in continental
Southern Africa
Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...
. That changed when, in 1882,
Baker
A baker is a tradesperson who bakes and sometimes sells breads and other products made of flour by using an oven or other concentrated heat source. The place where a baker works is called a bakery.
History
Ancient history
Since grains ha ...
contributed the first species accepted into the genus from
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
. The degree of
speciation
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...
then turned to
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, where the count of species far exceeds those on the mainland.
In 1907,
Costantin and
Bois constructed the first
monograph
A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject.
In library cataloging, ''monograph ...
, of ''Pachypodium'', in which they enumerated 17 species, where ten were from
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
and seven were from continental southern Africa.
Natural history
There is no
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
records of ''Pachypodium'' known. Yet certain conclusions can be drawn from the geology of the landscape in Madagascar as to the past
natural history of ''Pachypodium''.
Vernacular name
In southern Africa it is called the ''Kudu Lily''.
[Kudu Lil]
/ref>
References
Bibliography
*Eggli, Urs. (1993) Glossary of botanical terms with special reference to Succulent Plants. with German Equivalents (British Cactus & Succulent Society: United Kingdom)
*
*Endress, Mary: "The unification of Asclepiadaceae and Apocynaceae." ''Haseltonia: The Cactus and Succulent Society of America's Yearbook'' Vol. 8.
*Lavranos, John, J. (2004) "Pachypodium makayense: A New Species From Madagascar". ''Cactus and Succulent Journal'': United States 76 (2) 85-88.
*Lüthy, Jonas M. "Another look at the pachypodiums of Madagascar." Bradleya: The British Cactus and Succulent Society Yearbook. (22/2004)
*Mays, Harry. uropean Union Honorary Representative"The Huntington Botanical Gardens' 2005 offering of International Succulent Introductions for the European Union." Posting(Woodsleigh, Moss Lane, St. Michaels on Wyre, Preston, PR3 0TY, UK: 2005)
*Rapanarivo, S.H.J.V., Lavranos, J.J., Leeuwenberg, A.J.M., and Röösli, W. Pachypodium (Apocynaceae): Taxonomy, habitats and cultivation "Taxonomic revision of the genus Pachypodium," S.H.J.V. Rapanarivo and J.J. Lavranos; "The habitats of Pachypodium species" S.H.J.V. Rapanarivo; "Cultivation" W. Röösli. (A.A. Balkema: Rotterdam, Brookfield, 1999) apanarivo et al.*Rowley, Gordon, D. Cactus Handbook 5: Pachypodium and Adenium (British Cactus and Succulent Society, (1983) 1999)
*Rowley, Gordon. Didiereaceae: "Cacti of the Old World" (The British Cactus and Succulent Society SCS
ScS (Sofa Carpet Specialist), is a home furnishings retailer in the United Kingdom, specialising in sofas, carpets and flooring, dining and occasional furniture.
History
ScS was established in Sunderland, Tyne and Wear in 1894, as a family own ...
1992)
*Rowley, G.D. "The Pachypodium rosulatum aggregate (Apocynaceae) - one species or several?" Bradleya: The British Cactus and Succulent Society Yearbook. (16/1998)
*Rapanarivo, S.H.J.V., Lavranos, J.J., Leeuwenberg, A.J.M., and Röösli, W. Pachypodium (Apocynaceae): Taxonomy, habitats and cultivation "Taxonomic revision of the genus Pachypodium," S.H.J.V. Rapanarivo and J.J. Lavranos; "The habitats of Pachypodium species" S.H.J.V. Rapanarivo; "Cultivation" W. Röösli. (A.A. Balkema: Rotterdam, Brookfield, 1999, p. 5) he rest of the list is based on Rapanarivo et al.(1999)*Rapanarivo et al. (1999) p. 5.
Further reading
*
{{Taxonbar, from=Q131519
Flora of Madagascar
Succulent plants
Apocynaceae genera