''Phratora polaris'' is a species of

leaf beetle The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...

found in the Nordic regions of Europe., occasionally in Scotland, and Iceland. Some authors have recorded it in central Europe, especially in the Alps. Historically, this species has occurred in Greenland. This beetle is found on willow (''

Salix Willows, also called sallows and osiers, from the genus ''Salix'', comprise around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found primarily on moist so ...

'') species in the southern part of its range. Populations in Lapland feed on birch.

Description

This small (3.7–5 mm) beetle is similar in size and shape to other species of ''

Phratora Phratora is a genus of Chrysomelidae, leaf beetles. It is synonymous to ''Phyllodecta'' . European ''Phratora'' species can be distinguished based on morphology of female genitalia., but they differ little in size and body form and most sho ...

''. Willow-feeding adults are typically metallic blue or green, but birch feeding populations are metallic dark brown Larvae are dark to black and pupae are pale.

Distribution and range

''Phratora polaris'' occurs in the Nordic regions of Europe, occasionally in Scotland, and Iceland. It has also been recorded in the eastern Alps. and in Germany.

Habitat and host plants

''Phratora polaris'' is the only ''Phratora'' species known to feed on host plants in two different plant families (

Salicaceae The Salicaceae is the willow family of flowering plants. The traditional family (Salicaceae ''sensu stricto'') included the willows, poplar, aspen, and cottonwoods. Genetic studies summarized by the Angiosperm Phylogeny Group (APG) have greatly ...

) and (

Betulaceae Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams numbering a total of 167 species. They are mostly natives of the t ...

). In most of its range, ''P. polaris'' adults and larvae feed and lay eggs on willow (''

'') plants. In Iceland, Norway and Scotland, populations are found on the low-growing ''

Salix herbacea ''Salix herbacea'', the dwarf willow, least willow or snowbed willow, is a species of tiny creeping willow (family Salicaceae) adapted to survive in harsh arctic and subarctic environments. Distributed widely in alpine and arctic environments ar ...

''. In Norway and Finland, populations occur on the tea-leaved willow (''

Salix phylicifolia ''Salix phylicifolia'', the tea-leaved willow, is a species of willow native to Northern Europe including Iceland, the Faroe Islands, Scandinavia, Finland, Russia, and Western Siberia. It was the first bush found on the new volcanic island of Sur ...

'') and on ''

Salix polaris ''Salix polaris'', the polar willow, is a species of willow with a circumpolar distribution in the high arctic tundra, extending north to the limits of land, and south of the Arctic in the mountains of Norway, the northern Ural Mountains, the no ...

''. In Alpine Austria, it has been recorded on ''

Salix arbuscula ''Salix arbuscula'', the mountain willow, is a low, much branched shrub (to 0.7 metres) having a limited distribution in Northern Europe, occurring from north Scandinavia eastwards to Siberia. In Scotland it can be found on damp rocky mountain sl ...

''. In Finnish Lapland and Swedish Lapland, ''P. polaris'' is known to feed on ''

Betula pubescens ''Betula pubescens'' (syn. ''Betula alba''), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia ...

''.

Taxonomy

Phratora polaris female genitalia Valtimo Finland

''Phratora polaris'' is closely related to ''

Phratora tibialis ''Phratora tibialis'' is a species of leaf beetle found in Europe and parts of Asia. This beetle is found on willows (''Salix'' species) and the chemistry and production of its larval defensive secretions and host plant relationships have been stu ...

'', as noted by Palmen, Steinhausen, Sundholm, and Köpf et al. (1996). Male and female genitalia of ''P. polaris'' (which can be observed with live beetles under the dissecting scope when pressure is applied to the abdomen), closely resemble those of '' P. tibialis''. Steinhausen (1993) described populations in Austria as belonging to a 'boreal-alpine' form of ''P. polaris''. Phratora phylogeny

Mitochondrial sequences at the mitochondrial ''

cytochrome c oxidase subunit I Cytochrome c oxidase I (COX1) also known as mitochondrially encoded cytochrome c oxidase I (MT-CO1) is a protein that in humans is encoded by the ''MT-CO1'' gene. In other eukaryotes, the gene is called ''COX1'', ''CO1'', or ''COI''. Cytochrom ...

'' (DNA barcoding) gene show more divergence among willow- vs birch-feeding populations of ''P. polaris'' within Finland than between willow-feeding populations of ''P. polaris'' from Finland and ''P. tibialis'' from Switzerland. In 1996, Köpf et al. examined host plant preferences and mating behaviors for ''P. tibialis'' populations from Switzerland and a ''P. polaris'' population in eastern Finland. Beetles from all three populations showed similar host plant preferences, regardless of the host plant that they had been collected on, and ''P. tibialis'' and ''P. polaris'' individuals also mated with each other freely. These behavioral studies suggest that the actual biological species boundaries may be different than current classifications suggest. For example, birch-feeding populations of ''P. polaris'' might be classified as different species.

Life history and natural enemies

Like other ''

'' species at high altitudes and latitudes, ''P. polaris'' probably undergoes one generation within a growing season. It probably shares the same natural enemies as other

species, which are described in more detail for ''

Phratora vitellinae ''Phratora vitellinae'', the brassy leaf beetle, formerly ''Phyllodecta vitellinae'', is a beetle of the family Chrysomelidae found in Europe and Asia. It feeds on ''Populus'' and ''Salix'' species. The evolution of its host plant preferences and ...

'' and ''

Phratora laticollis ''Phratora laticollis'' is a species of Chrysomelidae, leaf beetle found in Europe and Asia. This beetle is found on ''Populus'' species and the chemistry and production of its larval defensive secretions and host plant relationships have been st ...

''.

Larval secretion chemistry

''Phratora polaris'' larvae secrete a defensive secretion that contains iridoid monoterpenes that they synthesize themselves (autogeneously), while their congener ''

'' sequesters host plant salicylates to make its larval defensive secretion. Using host plant compounds to make the larval defensive secretions appears to be the evolutionarily advanced or derived state of this trait. Studies of the effect of these defensive secretions on potential generalist spider predators revealed that the spiders ate larvae of ''P. polaris'' more readily than ''P. vitellinae'', which was probably because the defensive secretion of ''

'' was more repellent to the spiders than the secretion of ''P. polaris''.

References

External links

Images representing ''Phratora''
at

BOLD In typography, emphasis is the strengthening of words in a text with a font in a different style from the rest of the text, to highlight them. It is the equivalent of prosody stress in speech. Methods and use The most common methods in W ...

{{Taxonbar, from=Q3327855 Chrysomelinae Beetles of Europe Beetles described in 1886