Climate shapes the spatiotemporal variation in color morph diversity and composition across the distribution range of Chrysomela lapponica leaf beetle.

Color polymorphism offers rich opportunities for studying the eco-evolutionary mechanisms that drive the adaptations of local populations to heterogeneous and changing environments. We explored the color morph diversity and composition in a Chrysomela lapponica leaf beetle across its entire distribution range to test the hypothesis that environmental and climatic variables shape spatiotemporal variation in the phenotypic structure of a polymorphic species. We obtained information on 13 617 specimens of this beetle from museums, private collections, and websites. These specimens (collected from 1830-2020) originated from 959 localities spanning 33° latitude, 178° longitude, and 4200 m altitude. We classified the beetles into five color morphs and searched for environmental factors that could explain the variation in the level of polymorphism (quantified by the Shannon diversity index) and in the relative frequencies of individual color morphs. The highest level of polymorphism was found at high latitudes and altitudes. The color morphs differed in their climatic requirements; composition of colour morphs was independent of the geographic distance that separated populations but changed with collection year, longitude, mean July temperature and between-year temperature fluctuations. The proportion of melanic beetles, in line with the thermal melanism hypothesis, increased with increasing latitude and altitude and decreased with increasing climate seasonality. Melanic morph frequencies also declined during the past century, but only at high latitudes and altitudes where recent climate warming was especially strong. The observed patterns suggest that color polymorphism is especially advantageous for populations inhabiting unpredictable environments, presumably due to the different climatic requirements of coexisting color morphs.

Review of leaf beetles from the genus Entomoscelis (Coleoptera: Chrysomelidae) in Kazakhstan and Central Asia.

From the leaf beetle genus Entomoscelis only E. adonidis (Pallas) has been reliably recorded for Kazakhstan and major parts of Central Asia so far. Distribution of E. adonidis is first mapped in Kazakhstan in connection to natural zonation. Besides, the records of this species in Central Asia are summarized, southern and south-eastern borders of its distribution area are first clearly demonstrated. E. pilula Lopatin described from Azerbaijan and hitherto known only from the Caucasus is first recorded from Western Kazakhstan. E. sacra is recorded from South Kazakhstan and for the first time from South Urals in Russia and Ukraine. The identity of E. sacra is discussed. A key is provided for the Entomoscelis species from Kazakhstan and Central Asia. Trans-Caspian type of distribution of E. pilula is discussed from a zoogeographical point of view.

A chromosomal analysis of twelve species of the subfamily Chrysomelinae (Coleoptera, Chrysomelidae).

Twelve species of chrysomelines, all but one from the Palaearctic region, have been cytogenetically analyzed, mostly through their male meiotic metaphases I. Ambrostoma superbum has 2n = 40 (Xy(p)), Chrysolina colasi, Oreina fairmairiana and the Neotropical Platyphora spectabilis have 2n = 24 (Xy(p)), Chrysolina gebleri 2n = 26 (XY(p)), Colaspidema barbarum 2n = 28 (Xy(p)), Crosita altaica and C. rugulosa 2n = 30 (Xy(p)), Phratora polaris, Ph. vitellinae and Ph. vulgatissima 2n = 34 (Xy(p)), and the karyotype of Chrysolina marginata, consisting of 40 chromosomes, is also described. These results are discussed with those previously obtained in related genera and congeneric species, giving further support and extending the high chromosomal variability so far found in this subfamily of leaf beetles.

Review of the genus Cystocnemis (Coleoptera: Chrysomelidae: Chrysomelinae) with descriptions of two new species .

Two new species of Cystocnemis (s. str.) Motschulsky, 1860 namely C. levmedvedevi sp. nov. and C. zintshenkoi sp. nov. are described from the Mongolian Altai (Mongolia, Hovd aimag) and Southern Altai (Kazakhstan, East-Kazakhstan region) respectively. Generic diagnosis as well as key to species and subspecies of Cystocnemis are provided. Zoogeographical affinities of Entomoscelini are discussed.

Conflicting mitochondrial and nuclear phylogeographic signals and evolution of host-plant shifts in the boreo-montane leaf beetle Chrysomela lapponica.

We conducted a phylogeographic study on the cold-adapted leaf beetle Chrysomela lapponica, that feeds on willow or birch, by sampling several populations throughout most of the geographic distribution of the species, and by sequencing for each individual one mitochondrial and two nuclear DNA fragments. Patterns of DNA sequence variation from the mitochondrial and nuclear loci, as displayed in the median-joining networks, appear to display contradicting historical signal: a deep genealogical divergence is observed with the mitochondrial genome between the Alpine population and all other populations found in the Euro-Siberian distribution of the species, that is completely absent with both nuclear loci. We use coalescence simulations of DNA sequence evolution to test the hypothesis that this apparent conflict is compatible with a neutral model of sequence evolution (i.e., to check whether the stochastic nature of the coalescence process can explain these patterns). Because the simulations show that this is highly unlikely, we consider two alternative hypotheses: (1) introgression of the mitochondrial genome of another species and (2) the effect of natural selection. Although introgression is the most plausible explanation, we fail to identify the source species of the introgressed mitochondrial genome among all known species closely related to C. lapponica. We therefore suggest that the putative introgression event is ancient and the source species is either extinct or currently outside the geographic range of C. lapponica explored in this study. The observed DNA sequence variation also suggests that a host-plant shift from willow to birch has occurred recently and independently in each of the three birch-feeding populations. This emphasizes further the relative ease with which these beetles can escape their ancestral host-plant specialization on willow, but shows at the same time that host-plant shifts are highly constrained, as they only occur between willow and birch.

Testing phylogeographic hypotheses in a Euro-Siberian cold-adapted leaf beetle with coalescent simulations.

Few studies to date have investigated the impact of Pleistocene climatic oscillations on the genetic diversity of cold-adapted species. We focus on the geographic distribution of genetic diversity in a Euro-Siberian boreo-montane leaf beetle, Gonioctena pallida. We present the molecular variation from three independent gene fragments over the entire geographic range of this insect. The observed sequence variation identifies a genetic diversity hot spot in the Carpathian Mountains, in central Europe, which reveals the presence of (1) an ancestral refuge population or (2) a secondary contact zone in this area. Modeling of population evolution in a coalescent framework allowed us to favor the ancestral refuge hypothesis. These analyses suggest that the Carpathian Mountains served as a refuge for G. pallida, whereas the rest of the species distribution, that spans a large portion of Europe and Asia, experienced a dramatic reduction in genetic variation probably associated to bottlenecks and/or founder events. We estimated the time of isolation of the ancestral refuge population, using an approximate Bayesian method, to be larger than 90,000 years. If true, the current pattern of genetic variation in this cold-adapted organism was shaped by a climatic event predating by far the end of the last ice age.