The role of geography and ecology in shaping repeated patterns of morphological and genetic differentiation between European minnows (Phoxinus phoxinus) from the Pyrenees and the Alps

Neutral and selective processes can drive repeated patterns of evolution in different groups of populations experiencing similar ecological gradients. In this paper, we used a combination of nuclear and mitochondrial DNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological and genetic divergence of European minnows in two mountain ranges: the Pyrenees and the Alps. European minnows (Phoxinus phoxinus) are cyprinid fish inhabiting most freshwater bodies in Europe, including those in different mountain ranges that could act as major geographical barriers to gene flow. We explored patterns of P. phoxinus phenotypic and genetic diversification along a gradient of altitude common to the two mountain ranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation (IBA). The results indicated that populations from the Pyrenees and the Alps belong to two well differentiated, reciprocally monophyletic mtDNA lineages. Substantial genetic differentiation due to geographical isolation within and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPs markers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Also, morphology varied strongly with elevation and so did genetic differentiation to a lower extent. Despite moderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneity was found at the genetic level, suggesting that selection and population specific genetic drift act in concert to affect genetic divergence.     

Microbial eukaryote plankton communities of high‐mountain lakes from three continents exhibit strong biogeographic patterns

Microbial eukaryotes hold a key role in aquatic ecosystem functioning. Yet, their diversity in freshwater lakes, particularly in high‐mountain lakes, is relatively unknown compared with the marine environment. Low nutrient availability, low water temperature and high ultraviolet radiation make most high‐mountain lakes extremely challenging habitats for life and require specific molecular and physiological adaptations. We therefore expected that these ecosystems support a plankton diversity that differs notably from other freshwater lakes. In addition, we hypothesized that the communities under study exhibit geographic structuring. Our rationale was that geographic dispersal of small‐sized eukaryotes in high‐mountain lakes over continental distances seems difficult. We analysed hypervariable V4 fragments of the SSU rRNA gene to compare the genetic microbial eukaryote diversity in high‐mountain lakes located in the European Alps, the Chilean Altiplano and the Ethiopian Bale Mountains. Microbial eukaryotes were not globally distributed corroborating patterns found for bacteria, multicellular animals and plants. Instead, the plankton community composition emerged as a highly specific fingerprint of a geographic region even on higher taxonomic levels. The intraregional heterogeneity of the investigated lakes was mirrored in shifts in microbial eukaryote community structure, which, however, was much less pronounced compared with interregional beta‐diversity. Statistical analyses revealed that on a regional scale, environmental factors are strong predictors for plankton community structures in high‐mountain lakes. While on long‐distance scales (>10 000 km), isolation by distance is the most plausible scenario, on intermediate scales (up to 6000 km), both contemporary environmental factors and historical contingencies interact to shift plankton community structures.     

THE GEOGRAPHY OF COEVOLUTION: COMPARATIVE POPULATION STRUCTURES FOR A SNAIL AND ITS TREMATODE PARASITE

Gene flow and the genetic structure of host and parasite populations are critical to the coevolutionary process, including the conditions under which antagonistic coevolution favors sexual reproduction. Here we compare the genetic structures of different populations of a freshwater New Zealand snail (Potamopyrgus antipodarum) with its trematode parasite (Microphallus sp.) using allozyme frequency data. Allozyme variation among snail populations was found to be highly structured among lakes; but for the parasite there was little allozyme structure among lake populations, suggesting much higher levels of parasite gene flow. The overall pattern of variation was confirmed with principal component analysis, which also showed that the organization of genetic differentiation for the snail (but not the parasite) was strongly related to the geographic arrangement of lakes. Some snail populations from different sides of the Alps near mountain passes were more similar to each other than to other snail populations on the same side of the Alps. Furthermore, genetic distances among parasite populations were correlated with the genetic distances among host populations, and genetic distances among both host and parasite populations were correlated with “stepping-stone” distances among lakes. Hence, the host snail and its trematode parasite seem to be dispersing to adjacent lakes in a stepping-stone fashion, although parasite dispersal among lakes is clearly greater. High parasite gene flow should help to continuously reintroduce genetic diversity within local populations where strong selection might otherwise isolate “host races.” Parasite gene flow can thereby facilitate the coevolutionary (Red Queen) dynamics that confer an advantage to sexual reproduction by restoring lost genetic variation.     

To hybridize or not to hybridize: what separates two genetic lineages of the Chalk‐hill Blue Polyommatus coridon (Lycaenidae,Lepidoptera) along their secondary contact zone throughout eastern Central Europe?

As a consequence of postglacial range expansion, hybrid zones evolved where different genetic lineages met. In this study, we analysed the Chalk‐hill Blue Polyommatus coridon all along the contact zone of two expansive lineages. This zone stretches from the sandy areas of north‐eastern Germany, along the mountain ranges of the German–Czech border and throughout the eastern Alps. We studied allozymes (19 loci) of 38 populations (1542 individuals) and compared these data sets against 15 populations of the western and 15 populations of the eastern lineages and found different degrees of hybridization. Thus, the calcareous regions of Thuringia and Sachsen‐Anhalt were mostly colonized by the western lineage. The middle mountain ranges between Bavaria and Bohemia represented a strong barrier blocking further expansion and thus completely impeding hybridization in this region. More intense hybridization was detected in the populations of the eastern Alps, especially in the north‐eastern part, where the Danube most probably acted as an expansion corridor for both lineages followed by intensive hybridization. In the south‐eastern Alps, hybrid populations were mostly detected in the easternmost parts and along the larger river valley of Drava and Mur; pure western populations dominated in the other areas of this region. These results show that the degree of hybridization along a contact zone is correlated with the ecological demands of a species and the regional physical geographic circumstances. This finding was proved for the Chalk‐hill Blue in our study but is also the most likely scenario in most animal and plant species.     

Effects of recent and past climatic shifts on the genetic structure of the high mountain Yellow‐spotted ringlet butterfly Erebia manto (Lepidoptera,Satyrinae): a conservation problem

Mountain species have evolved important genetic differentiation due to past climatic fluctuations. The genetic uniqueness of many of these lineages is now at risk due to global warming. Here, we analyse allozyme polymorphisms of 1306 individuals (36 populations) of the mountain butterfly Erebia manto and perform Species Distribution Models (SDMs). As a consensus of analyses, we obtained six most likely genetic clusters: (i) Pyrenees with Massif Central; (ii) Vosges; (iii–v) Alps including the Slovakian Carpathians; (vi) southern Carpathians. The Vosges population showed the strongest genetic split from all other populations, being almost as strong as the split between E. manto and its sister species Erebia eriphyle. The distinctiveness of the Pyrenees‐Massif Central group and of the southern Carpathians group from all other groups is also quite high. All three groups are assumed to have survived more than one full glacial–interglacial cycle close to their current distributions with up‐hill and down‐slope shifts conforming climatic conditions. In contrast with these well‐differentiated groups, the three groups present in the Alps and the Slovakian Carpathians show a much shallower genetic structure and thus also should be of a more recent origin. As predicted by our SDM projections, rising temperatures will strongly impact the distribution of E. manto. While the populations in the Alps are predicted to shrink, the survival of the three lineages present here should not be at risk. The situation of the three other lineages is quite different. All models predict the extinction of the Vosges lineage in the wake of global warming, and also the southern Carpathians and Pyrenees‐Massif Central lineages might be at high risk to disappear. Thus, albeit global warming will therefore be unlikely to threaten E. manto as a species, an important proportion of the species’ intraspecific differentiation and thus uniqueness might be lost.     

Differentiation and speciation in mountain streams: a case study in the caddisfly Rhyacophila aquitanica (Trichoptera)

Few studies have analysed the biogeography of mountain aquatic organisms, although this habitat provides stable conditions in which many species survived Pleistocene climatic oscillations, usually in the geographical vicinity of their present distribution ranges. The mountain caddisfly Rhyacophila aquitanica was selected as a model organism for this habitat type. Morphological measurements of genitalia and external characters of male individuals were obtained from almost the entire range of distribution of the species. Morphometric results were analysed by cluster analysis and multivariate statistics. Important differences were discovered among three population groups of R. aquitanica inhabiting different European mountain ranges: (i) mountain ranges north‐west of the Alps (Massif Central, Vosges, Schwarzwald and Fribourg); (ii) the southern Alps (Lombardia and Carinthia); and (iii) the western part of the southern Carpathians. This divergence suggests a long‐term isolation among these groups, which presumably took place long before the last Pleistocene glaciation, with no secondary contact among these populations. The differentiation centres of the southern Alps and Carpathian groups may have been mostly homotopic to their actual ranges, whereas the western group must have been distributed in the areas west or north‐west of the Alps with secondary expansions and disjunctions.     

Congruent patterns of lineage diversity in two species complexes of planktonic crustaceans,Daphnia longispina (Cladocera) and Eucyclops serrulatus (Copepoda), in East European mountain lakes

Cladocerans and copepods are globally important freshwater zooplankton groups, differing in reproductive modes and dispersal abilities. We compared genetic variation of two common taxa of these crustaceans, the Daphnia longispina species complex (known to harbour multiple cryptic lineages) and Eucyclops serrulatus (morphologically and ecologically variable morphospecies), in lakes of ten Eastern European mountain ranges. We expected to discover cryptic lineages in both groups, and to observe different geographical patterns of diversity because of differences in life cycles. Within E. serrulatus, limited sampling through lowland habitats indeed showed the presence of eight highly divergent clades, probably cryptic species, but most of these were not found in the studied mountain lakes. Such a pattern was congruent with the diversity of the D. longispina complex. Regional coexistence of multiple clades within respective species complexes (two in Eucyclops and three in Daphnia) was observed only in the Tatra Mountains (on the Polish?Slovak border). In all other studied mountain ranges (in the Balkans), only single lineages of Daphnia and Eucyclops, respectively, were present, showing similar intraspecific patterns and no evidence for stronger dispersal limitation in Eucyclops than in Daphnia. Our results indicate that substantial cryptic variation may be expected in seemingly widespread copepod taxa. However, detection of cryptic lineages is not a general pattern in mountain lakes, although these habitats harbour substantial genetic diversity in crustacean zooplankton. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 754–767.     

Genomic and phenotypic differentiation of Arabidopsis thaliana along altitudinal gradients in the North Italian Alps

Altitudinal gradients in mountain regions are short‐range clines of different environmental parameters such as temperature or radiation. We investigated genomic and phenotypic signatures of adaptation to such gradients in five Arabidopsis thaliana populations from the North Italian Alps that originated from 580 to 2350 m altitude by resequencing pools of 19–29 individuals from each population. The sample includes two pairs of low‐ and high‐altitude populations from two different valleys. High‐altitude populations showed a lower nucleotide diversity and negative Tajima's D values and were more closely related to each other than to low‐altitude populations from the same valley. Despite their close geographic proximity, demographic analysis revealed that low‐ and high‐altitude populations split between 260 000 and 15 000 years before present. Single nucleotide polymorphisms whose allele frequencies were highly differentiated between low‐ and high‐altitude populations identified genomic regions of up to 50 kb length where patterns of genetic diversity are consistent with signatures of local selective sweeps. These regions harbour multiple genes involved in stress response. Variation among populations in two putative adaptive phenotypic traits, frost tolerance and response to light/UV stress was not correlated with altitude. Taken together, the spatial distribution of genetic diversity reflects a potentially adaptive differentiation between low‐ and high‐altitude populations, whereas the phenotypic differentiation in the two traits investigated does not. It may resemble an interaction between adaptation to the local microhabitat and demographic history influenced by historical glaciation cycles, recent seed dispersal and genetic drift in local populations.     

Speciation of silverside Chirostoma attenuatum (Pisces: Atheriniformes) in Central Mexico

The high speciation rate of Chirostoma in Central Mexico has been associated with allopatric speciation events promoted by the emergence of vicariant barriers in freshwater habitats, as well as by sympatric ecological segregation, common in those species inhabiting lacustrine ecosystems. Through nuclear and mitochondrial markers, this study revealed a speciation process within Chirostoma attenuatum resulting in two evolutionary independent units that coincide with their morphological differentiation, indicating that Chirostoma attenuatum and Chirostoma zirahuen may be considered separate species. This process was the result of vicariance associated with geological dynamics of the region. Phylogeographic findings indicated two speciation stages: early allopatric isolation, during which the isolated populations accumulated unique adaptations, and secondary contact with low migration rate and the maintenance of the evolutionary trajectory. Historical demographic analysis indicated that the two well‐differentiated lineages underwent independent evolutionary histories in their respective lakes. Chirostoma zirahuen from Zirahuen and C. attenuatum from Patzcuaro represent unique and irreplaceable genetic diversity that must to be conserved.     

At the edge and on the top: molecular identification and ecology of Daphnia dentifera and D. longispina in high-altitude Asian lakes

The occurrence of members of the highly diverse Daphnia longispina complex in Southern and Central Asian high-mountain lakes has been recognized for more than a century. Until now, however, no molecular data have been available for these populations inhabiting the “Roof of the World.” Here, we present the first identification for D. gr. longispina from that region based on a molecular phylogeny. Our findings show that alpine lakes in the Pamir and Himalaya mountains host populations of widespread species of the complex, for which these are the highest known localities. A spineless morph from the Himalaya region, previously labeled as D. longispina var. aspina, was clustering tightly with D. dentifera, while a population from the Pamir mountain range was grouped with D. longispina. In addition, we analyzed ecological data available for lakes in the Khumbu region (Himalaya) to investigate ecological preferences of non-pigmented D. gr. longispina. The identified factors can at least partly be related to avoidance of high UV conditions by this species. We conclude that the widespread species D. dentifera and D. longispina also colonized the Asian high-mountain lakes, and identify the need for further research to trace the possible effect of rapid environmental changes in this region on the diversity and ecology of high-altitude Daphnia populations.     

Southern isolation and northern long‐distance dispersal shaped the phylogeography of the widespread,but highly disjunct,European high mountain plant Artemisia eriantha (Asteraceae)

We investigated the range dynamics of Artemisia eriantha, a widespread, but rare, mountain plant with a highly disjunct distribution in the European Alpine System. We focused on testing the roles of vicariance and long‐distance dispersal in shaping the current distribution of the species. To this end, we collected AFLP and plastid DNA sequence data for 17 populations covering the entire distributional range of the species. Strong phylogeographical structure was found in both datasets. AFLP data suggested that almost all populations were genetically strongly differentiated, with 58% of the overall genetic variation partitioned among populations. Bayesian clustering identified five groups of populations: Balkans, Pyrenees, Central Apennines, one southwestern Alpine population and a Widespread cluster (eastern Pyrenees, Alps, Carpathians). Major groups were supported by neighbor‐joining and NeighbourNet analyses. Fourteen plastid haplotypes were found constituting five strongly distinct lineages: Alps plus Pyrenees, Apennines, Balkans, southern Carpathians, and a Widespread group (eastern Pyrenees, northern Carpathians, Mt. Olympus). Plastid DNA data suggested that A. eriantha colonized the European Alpine System in a westward direction. Although, in southern Europe, vicariant differentiation among the Iberian, Italian and Balkan Peninsulas predominated, thus highlighting their importance as glacial refugia for alpine species, in temperate mountain ranges, long‐distance dispersal prevailed. This study emphasizes that currently highly disjunct distributions can be shaped by both vicariance and long‐distance dispersal, although their relative importance may be geographically structured along, for instance, latitude, as in A. eriantha. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174 , 214–226.     

The wide but disjunct range of the European mountain plant Androsace lactea L. (Primulaceae) reflects Late Pleistocene range fragmentation and post‐glacial distributional stasis

Aim Our aim was to reconstruct the spatio‐temporal genetic diversification of Androsace lactea, a widely but disjunctly distributed European mountain plant, to test the hypothesis that its distribution is the result of vicariance, in the late Tertiary or during the Pleistocene, or alternatively of long‐distance dispersal. We also addressed the phylogeographic history of the Alps, emphasizing the role of Pleistocene refugia at their northern margin. Location The central and southern European mountain ranges. Methods We gathered amplified fragment length polymorphism (AFLP) data and plastid DNA sequences from one to four individuals of each of 26 populations spanning the entire distribution area. AFLP data were analysed with Bayesian clustering approaches, neighbour‐joining analysis and NeighbourNet. Plastid sequences were used to depict relationships among haplotypes in a statistical parsimony network, to test for population expansions, and to obtain age estimates in a Bayesian framework. Results The AFLP data suggested that many populations were genetically strongly differentiated. The internal structure, however, was weak, and only two major groups of populations, from the north‐western Alps and adjacent regions and from the easternmost Alps, were supported in the neighbour‐joining analysis. One of the Bayesian clustering approaches differentiated three groups of populations: Northern Alps, easternmost Alps and the remaining distribution area. Eleven closely related plastid haplotypes were found, separated by maximally four mutational steps, resulting in a star‐like parsimony network. None of several estimators suggested statistically significant population expansions. The diversification age was inferred to be (mean/median) 0.135/0.08 Ma (95% highest posterior density interval 0.364–0.006 Ma). Main conclusions We found no evidence that long‐distance dispersal shaped the disjunct distribution range; our data rather favoured a vicariance scenario. However, in contrast to the hypothesis that wide but disjunct distributions are old, we conclude that range fragmentation probably happened in the Late Pleistocene, perhaps during the last glaciation. In the Alps, most populations are at least close to formerly unglaciated areas. Our data support distributional stasis and suggest that important refugia were situated at the north‐eastern, but also at the northern and north‐western edges of the Alps, thereby strengthening the evidence for glacial refugia in this strongly glaciated region.     

Ecological genetics of Norwegian Daphnia. II. Distribution of Daphnia longispina genotypes in relation to short-wave radiation and water colour

In the mountain range of South Norway, transparent and melanic members of the Daphnia longispina complex occur. Melanic populations inhabit clearwater lakes and ponds, while transparent populations are found in ponds with slightly humic water. Mixed populations have not been detected. The distribution patterns of the two morphs are related to ambient levels of short-wave radiation, and the light absorptive properties of the inhabited waters. The pigment present is probably melanin, which is deposited in the dorsally directed parts of the carapace, head shield and antennae. Allozyme studies indicate that these distinct morphs are only remotely related, the alpine transparent group being closer to lowland, likewise transparent, populations. A melanic population found at Svalbard is closely related to the melanic mainland populations. Clonal diversity in ponds and shallow lakes is very low, in contrast to populations of deeper lakes.Deceased.     

Daphnia curvirostris Eylmann in Japanese high mountain waters (Cladocera: Daphniidae)

A species of Daphnia, Daphnia curvirostris Eylmann, found in high mountain lakes and ponds in central Japan is described. Although there were some differences in the shape of the male rostrum and the chromosome number between European populations as described by Johnson (1952) and Trentini (1980), and Japanese ones collected from high mountain waters, Japanese specimens had many characteristics similar to the taxon D. curvirostris of Europe.     

The extreme disjunction between Beringia and Europe in Ranunculus glacialis s. l. (Ranunculaceae) does not coincide with the deepest genetic split – a story of the importance of temperate mountain ranges in arctic–alpine phylogeography

The arctic–alpine Ranunculus glacialis s. l. is distributed in high‐mountain ranges of temperate Europe and in the North, where it displays an extreme disjunction between the North Atlantic Arctic and Beringia. Based on comprehensive sampling and employing plastid and nuclear marker systems, we (i) test whether the European/Beringian disjunction correlates with the main evolutionary diversification, (ii) reconstruct the phylogeographic history in the Arctic and in temperate mountains and (iii) assess the susceptibility of arctic and mountain populations to climate change. Both data sets revealed several well‐defined lineages, mostly with a coherent geographic distribution. The deepest evolutionary split did not coincide with the European/Beringian disjunction but occurred within the Alps. The Beringian lineage and North Atlantic Arctic populations, which reached their current distribution via rapid postglacial colonization, show connections to two divergent pools of Central European populations. Thus, immigration into the Arctic probably occurred at least twice. The presence of a rare cpDNA lineage related to Beringia in the Carpathians supports the role of these mountains as a stepping stone between temperate Europe and the non‐European Arctic, and as an important area of high‐mountain biodiversity. The temperate and arctic ranges presented contrasting phylogeographic histories: a largely static distribution in the former and rapid latitudinal spread in the latter. The persistence of ancient lineages with a strictly regional distribution suggests that the ability of R. glacialis to survive repeated climatic changes within southern mountain ranges is greater than what recently was predicted for alpine plants from climatic envelope modelling.     

The killer shrimp,Dikerogammarus villosus,invading European Alpine Lakes: A single main source but independent founder events with an overall loss of genetic diversity

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Phylogeography and recolonization of the Swiss Alps by the Valais shrew (Sorex antinorii), inferred with autosomal and sex‐specific markers

Using one male‐inherited, one female‐inherited and eight biparentally inherited markers, we investigate the population genetic structure of the Valais shrew (Sorex antinorii) in the Swiss Alps. Bayesian analysis on autosomal microsatellites suggests a clear genetic differentiation between two groups of populations. This geographically based structure is consistent with two separate postglacial recolonization routes of the species into Switzerland from Italian refugia after the last Pleistocene glaciations. Sex‐specific markers also confirm genetic structuring among western and eastern areas, since very few haplotypes for either Y chromosome or mtDNA genome are shared between the two regions. Overall, these results suggest that two already well‐differentiated genetic lineages colonized the Swiss Alps and came into secondary contact in the Rhône Valley. Low level of admixture between the two lineages is likely explained by the mountainous landscape structure of lateral valleys orthogonal to the main Rhône valley.     

Factor interaction influencing the distribution of the freshwater “shrimp” Gammarus

Summary The enormous variation in the environmental factors of south-eastern Norway makes this area particularly suitable for field studies on the relationship between environmental factors and fauna. Lakes are abundant, from 1 to 1,837 m a.s.l., and the geology of the surroundings as well as acid precipitation influence their chemical characteristics. In lowland areas the distribution of Gammarus lacustris is related to how rich in lime the lakes are. Populations found in mountain lakes tolerate much lower levels of calcium and higher H⁺ concentrations than populations inhabiting lowland lakes. The lowland populations probably have a higher calcium demand when stressed by high temperature. We predict that factor interaction may be used to explain the distribution patterns of the species also in other parts of Europe.     

Glacial refugia and postglacial expansion of the alpine–prealpine plant species Polygala chamaebuxus

The shrubby milkwort (Polygala chamaebuxus L.) is widely distributed in the Alps, but occurs also in the lower mountain ranges of Central Europe such as the Franconian Jura or the Bohemian uplands. Populations in these regions may either originate from glacial survival or from postglacial recolonization. In this study, we analyzed 30 populations of P. chamaebuxus from the whole distribution range using AFLP (Amplified Fragment Length Polymorphism) analysis to identify glacial refugia and to illuminate the origin of P. chamaebuxus in the lower mountain ranges of Central Europe. Genetic variation and the number of rare fragments within populations were highest in populations from the central part of the distribution range, especially in the Southern Alps (from the Tessin Alps and the Prealps of Lugano to the Triglav Massiv) and in the middle part of the northern Alps. These regions may have served, in accordance with previous studies, as long‐term refugia for the glacial survival of the species. The geographic pattern of genetic variation, as revealed by analysis of molecular variance, Bayesian cluster analysis and a PopGraph genetic network was, however, only weak. Instead of postglacial recolonization from only few long‐term refugia, which would have resulted in deeper genetic splits within the data set, broad waves of postglacial expansion from several short‐term isolated populations in the center to the actual periphery of the distribution range seem to be the scenario explaining the observed pattern of genetic variation most likely. The populations from the lower mountain ranges in Central Europe were more closely related to the populations from the southwestern and northern than from the nearby eastern Alps. Although glacial survival in the Bohemian uplands cannot fully be excluded, P. chamaebuxus seems to have immigrated postglacially from the southwestern or central‐northern parts of the Alps into these regions during the expansion of the pine forests in the early Holocene.     

Modes and mechanisms of a Daphnia invasion

Whether exotic species invade new habitats successfully depends on (i) a change in the invaded habitat that makes it suitable for the invader and (ii) a genetic change in the invading taxon that enhances its fitness in the new habitat, or both. We dissect the causes of invasions of Swiss lakes, north of the Alps, by Daphnia galeata (a zooplankter typical of eutrophic lakes, e.g. those south of the Alps, which are also warmer) by comparing the fitness performance of eight geographically distributed clones that were fed algal-food typical of oligotrophic versus eutrophic conditions at two temperatures. Daphnia longispina, native to oligotrophic Swiss lakes, served as a reference. Daphnia galeata requires eutrophic food to persist, whereas D. longispina survives and grows on oligotrophic food but does even better on eutrophic food. Invasion by D. galeata is further explained because invading clones from the north perform better on eutrophic food and at cooler temperatures than native clones from the south, suggesting a local response to countergradient selection. Our data support the hypothesis that populations of the invader in northern lakes are dominated by well-adapted genotypes. Our results illustrate how environmental change (i.e. eutrophication) and local adaptation can act together to drive a successful invasion.