Home-loving boreal hare mitochondria survived several invasions in Iberia: the relative roles of recurrent hybridisation and allele surfing

Genetic introgression from a resident species into an invading close relative can result from repeated hybridisation along the invasion front and/or allele surfing on the expansion wave. Cases where the phenomenon is massive and systematic, such as for hares (genus Lepus) in Iberia, would be best explained by recurrent hybridisation but this is difficult to prove because the donor populations are generally extinct. In the Pyrenean foothills, Lepus europaeus presumably replaced Lepus granatensis recently and the present species border is parallel to the direction of invasion, so that populations of L. granatensis in the contact zone represent proxies of existing variation before the invasion. Among three pairs of populations sampled across this border, we find less differentiation of mitochondrial DNA (mtDNA) across than along it, as predicted under recurrent hybridisation at the invasion front. Using autosomal microsatellite loci and X- and Y-linked diagnostic loci, we show that admixture across the border is quasi-absent, making it unlikely that lack of interspecific mtDNA differentiation results from ongoing gene flow. Furthermore, we find that the local species ranges are climatically contrasted, making it also unlikely that ongoing ecology-driven movement of the contact account for mtDNA introgression. The lack of mtDNA differentiation across the boundary is mostly due to sharing of mtDNA from a boreal species currently extinct in Iberia (Lepus timidus) whose mitochondria have thus remained in place since the last deglaciation despite successive invasions by two other species. Home-loving mitochondria thus witness past species distribution rather than ongoing exchanges across stabilised contact zones.     

Species distribution models contribute to determine the effect of climate and interspecific interactions in moving hybrid zones

Climate is a major factor delimiting species’ distributions. However, biotic interactions may also be prominent in shaping geographical ranges, especially for parapatric species forming hybrid zones. Determining the relative effect of each factor and their interaction of the contact zone location has been difficult due to the lack of broad scale environmental data. Recent developments in species distribution modelling (SDM) now allow disentangling the relative contributions of climate and species’ interactions in hybrid zones and their responses to future climate change. We investigated the moving hybrid zone between the breeding ranges of two parapatric passerines in Europe. We conducted SDMs representing the climatic conditions during the breeding season. Our results show a large mismatch between the realized and potential distributions of the two species, suggesting that interspecific interactions, not climate, account for the present location of the contact zone. The SDM scenarios show that the southerly distributed species, Hippolais polyglotta, might lose large parts of its southern distribution under climate change, but a similar gain of novel habitat along the hybrid zone seems unlikely, because interactions with the other species (H. icterina) constrain its range expansion. Thus, whenever biotic interactions limit range expansion, species may become ‘trapped’ if range loss due to climate change is faster than the movement of the contact zone. An increasing number of moving hybrid zones are being reported, but the proximate causes of movement often remain unclear. In a global context of climate change, we call for more interest in their interactions with climate change.     

Hares in Corsica: high prevalence of <Emphasis Type="Italic">Lepus corsicanus</Emphasis> and hybridization with introduced <Emphasis Type="Italic">L. europaeus</Emphasis> and <Emphasis Type="Italic">L. granatensis</Emphasis>

The Italian hare, Lepus corsicanus, was first described in Corsica more than 100 years ago, but the knowledge on the status of the species in this island remains scarce. Moreover, frequent introductions of thousands of individuals from other hare species, namely Lepus europaeus and Lepus granatensis, into Corsica are known to have occurred and an updated assessment of the prevalence of L. corsicanus in Corsica is therefore of utmost importance. Here, to estimate the relative prevalence of the hare species present in Corsica, we conducted a molecular analysis on 67 samples collected by hunters between 2002 and 2007 in 36 Corsican communes. Sequencing of portions of the nuclear gene transferrin and of the control region of the mitochondrial DNA allowed classifying most of the collected samples as belonging to L. corsicanus (70.1%). Of the sampled Corsican communes, 86.1% contained this species, while only in 11.1%, L. europaeus was present. Three of the analyzed specimens showed an inconsistent molecular assignment between markers suggesting a hybrid origin: L. corsicanus × L. europaeus, L. corsicanus × L. granatensis, and L. europaeus × L. granatensis. The first two cases of hybridization had never been described in nature, even in studies focusing on hares from Italy where L. corsicanus and L. europaeus are often sympatric. These results stress the real risk of corrosion of the native gene pool of L. corsicanus via hybridization with introduced species. We highlight the need of urgently rethinking the management plan of hare populations in Corsica.     

Speciation and paraphyly in western mediterranean hares (Lepus castroviejoi,L. europaeus,L. granatensis,andL. capensis) revealed by mitochondrial DNA phylogeny

Mitochondrial DNA (mtDNA) variation among specimens of the northwestern African hare (Lepus capensis schlumbergeri) and three European hares sampled in Spain (L. castroviejoi andL. granatensis, which are endemic to the Iberian Peninsula, andL. europaeus) was analyzed using seven restriction endonucleases. Fourteen haplotypes were found among the 34 animals examined. Restriction site maps were constructed and the phylogeny of the haplotypes was inferred. mtDNA ofL. capensis was the most divergent, which is consistent with its allopatric African distribution and with an African origin of European hares. We estimated that mtDNA in hares diverges at a rate of 1.5–1.8% per MY assuming that the European and African populations separated 5–6 MYBP. Maximum intraspecies nucleotide divergences were 1.3% inL. capensis, 2.7% inL. castroviejoi, and 2.3% inL. granatensis but 13.0% inL. europaeus. The latter species contained two main mtDNA lineages, one on the branch leading toL. castroviejoi and the other on that leading toL. granatensis. The separation of these two lineages from theL. castroviejoi orL. granatensis lineages appears to be much older than the first paleontological record ofL. europaeus in the Iberian peninsula. This suggests that the apparent polyphyly ofL. europaeus is due not to secondary introgression, but to the retention of ancestral polymorphism inL. europaeus. The results suggest thatL. europaeus either has evolved as a very large population for a long time or has been fractionated. Such a pattern of persistence of very divergent lineages has also been reported in other species of highly mobile terrestrial mammals. As far as mtDNA is concerned,L. europaeus appears to be the common phylogenetic trunk which has diversified during dispersion over the European continent and from whichL. castroviejoi andL. granatensis speciated separately in southwest Europe.     

Assessing biogeographical relationships of ecologically related species using favourability functions: a case study on British deer

Aim Using six free‐living deer species in Great Britain as a case study, we studied biogeographical relationships of ecologically related species composed of both native and introduced species. Location Great Britain. Methods  We modelled the environmental favourability for the deer species using variables related with spatial location, climate, topography, human disturbances and habitat structure. Favourability values of each pair of native (naturalized)‐introduced species were used to estimate the fuzzy overlap index (FOvI) as a measure of overall similarity between the environmental requirements for the species in Great Britain. The absolute local overlap values (FOvI‐L) were also used to measure the degree to which a given location was favourable simultaneously for each pair of species. We assessed the trends of species favourability across a range defined by the absolute local overlap values and studied the shape of the obtained curves since they informs us about the favourability balance between the studied species. Results Muntjac and Chinese water deer attained higher favourability values than native species in localities with intermediate values of FOvI‐L (a reduced number in the study area), suggesting that if competitive relationships were established in these localities the introduced deer species may have some advantages over natives. Sika deer only achieved higher values than fallow deer in those localities clearly unfavourable for the naturalized species. Our analyses predicted that fallow deer will be less affected by the introduced deer species than native species. Main conclusions We developed an approach based on the favourability function to describe biogeographical relationships between species, natives and introduced and to assess from a biogeographical perspective if introduced species could pose a competitive risk to natives. Although the results of present analyses do not conclusively demonstrate competitive exclusion, they provide directional hypotheses that can be tested in experimental field and laboratory studies.     

Diet of the Iberian hare (Lepus granatensis) in a mountain ecosystem

The diet of the Iberian hare (Lepus granatensis) was studied through microhistological pellet analysis in two areas from a mountain ecosystem in Central Portugal. Fecal pellets were collected monthly in 24 plots spatially distributed throughout the two study areas. For each period, a sample of 15 to 20 pellets was milled and 400 epidermal fragments were identified, by comparison with a reference collection. A wide range of plant species was observed in hare’s diet. Grasses represent the basis of the Iberian hare diet, with frequencies always higher than 50% in both study areas (annual average = 69.98%). Most of the 35 species of grasses assembled for the reference collection (91.43%) were identified in the pellets. Nevertheless, only six of these were consumed in proportions greater than 5%, being Anthoxanthum odoratum, Secale cereale and Agrostis spp. the species ingested in higher frequencies. The rate of grasses consumption reached 80.69% in winter but decreased in summer to around 55%. In this season, a concurrent rise in the ingestion of other plant groups, like herbs and shrubs, and of plant inflorescences was observed. This work provides the first results on the Iberian hare’s diet on mountain ecosystems, and suggests that the Iberian hare diet in a mountain ecosystem is similar to the observed in L. europaeus and L. timidus.     

Long term climate effects are confounded with the biological control programme against the invasive weed <Emphasis Type="Italic">Baccharis halimifolia</Emphasis> in Australia

Climate has an important influence on the distribution and abundance of invasive species. Habitat suitability for invasive plants could shift with a changing climate and management practices may need to shift in response. Anecdotal evidence suggests that groundsel bush (Baccharis halimifolia) has declined in abundance over the past 50 years in Australia, co-incident with the introduction of a suite of biological control agents. While biological control may be responsible for this decline, here we investigate an alternative hypothesis—that long-term change in the favourability of the climate may have changed growth conditions for groundsel bush throughout its Australian range. We also predict what may happen to the future distribution of this species, using a bioclimatic modelling technique (CLIMEX). We found a significant reduction in the favourability for growth of B. halimifolia over the past 50 years at 29 sites in Australia. Under a likely IPCC future climate scenario prediction (decrease in rainfall and increase in temperature), the favourability for growth of B. halimifolia will continue to decrease in Queensland and its distribution may move further south into New South Wales and Victoria. We conclude that climate alone may have had a significant effect on the distribution and abundance of B. halimifolia and future priorities for management of B. halimifolia should focus on its southern distribution. Determining the success of the biological control programme in isolation from the observed climate effects will be difficult. Given the likelihood of future climate change worldwide evaluation of biological control programmes in general will need to also account for climate effects.     

Influences of ecology and biogeography on shaping the distributions of cryptic species: three bat tales in Iberia

To determine what shapes the distributions of cryptic species, we aimed to unravel ecological niches and geographical distributions of three cryptic bat species complexes in Iberia, Plecotus auritus/begognae, Myotis mystacinus/alcathoe and Eptesicus serotinus/isabellinus (with 44, 69, 66, 27, 121 and 216 records, respectively), considering ecological interactions and biogeographical patterns. Species distribution models (SDMs) were built using a presence‐only technique (Maxent), incorporating genetically identified species records with environmental variables (climate, habitat, topography). The most relevant variables for each species’ distribution and respective response curves were then determined. SDMs for each species were overlapped to assess the contact zones within each complex. Niche analyses were performed using niche metrics and spatial principal component analyses to study niche overlap and breadth. The Plecotus complex showed a parapatric distribution, although having similar biogeographical affinities (Eurosiberian), possibly explained by competitive exclusion. The Myotis complex also showed Eurosiberian affinities, with high overlap between niches and distribution, suggesting resource partitioning between species. Finally, E. serotinus was associated with Eurosiberian areas, while E. isabellinus occurred in Mediterranean areas, suggesting possible competition in their restricted contact zone. This study highlights the relevance of considering potential ecological interactions between similarly ecological species when assessing species distributions. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 ,150–162.     

European hare (Lepus europaeus) invasion ecology: implication for the conservation of the endemic Irish hare (Lepus timidus hibernicus)

European hare Lepus europaeus populations have undergone recent declines but the species has successfully naturalised in many countries outside its native range. It was introduced to Ireland during the mid-late nineteenth century for field sport and is now well established in Northern Ireland. The native Irish hare Lepus timidus hibernicus is an endemic subspecies of mountain hare L. timidus and has attracted major conservation concern following a long-term population decline during the twentieth century and is one of the highest priority species for conservation action in Ireland. Little is known about the European hare in Ireland or whether it poses a significant threat to the native mountain hare subspecies by compromising its ecological security or genetic integrity. We review the invasion ecology of the European hare and examine evidence for interspecific competition with the mountain hare for habitat space and food resources, interspecific hybridisation, disease and parasite transmission and possible impacts of climate change. We also examine the impact that introduced hares can have on native non-lagomorph species. We conclude that the European hare is an emerging and significant threat to the conservation status of the native Irish hare. Invasive mammal species have been successfully eradicated from Ireland before and immediate action is often the only opportunity for cost-effective eradication. An urgent call is issued for further research whilst the need for a European hare invasive Species Action Plan (iSAP) and Eradication strategy are discussed.     

Diet selection by European hares (Lepus europaeus) in the alpine zone of the Snowy Mountains, Australia

European hares (Lepus europaeus) are grazers and open grassland specialists that are replaced in mountain areas of their natural range in the northern hemisphere by browsing/intermediate feeding mountain hares (Lepus timidus), but in their introduced range in the southern hemisphere, occupy the alpine zone. We used micro-histological identification of plant fragments and germination of seeds in faecal pellets of L. europaeus from the Snowy Mountains, Australia, to determine diet. We asked whether diet shifted and/or diet breadth expanded in response to seasonally reduced food availability, particularly during winter. If so, did the constraints of food availability in the alpine zone lead to the diet mirroring that of L. timidus in its native alpine habitat. The diet of L. europaeus was dominated by grasses, herbs and shrubs. The main diet items in summer were grasses (70 %) and herbs (28 %). Grasses declined in the diet between summer and autumn when herbs increased to co-dominance, with a further change after establishment of the winter snowpack to a greater preponderance of shrubs (43 % compared with a maximum of 3 % in snow-free months). L. europaeus selected a wider range of plants in winter (59 species compared with 39 in summer) and diet was significantly more variable in winter than in autumn or summer (and in autumn than summer). We concluded that the persistence of L. europaeus in alpine areas of the southern hemisphere is testament to their ability to expand their dietary breadth to occupy mountain climatic zones normally occupied by L. timidus.     

The role of climate for the range limits of parapatric European land salamanders

Abrupt range limits of parapatric species may serve as a model system to understand the factors that determine species’ range borders. Theory suggests that parapatric range limits can be caused by abiotic conditions along environmental gradients, biotic interactions or a combination of both. Geographic ranges of the parapatric salamanders, Salamandra salamandra and S. atra, meet in small contact zones in the European Alps and to date, the cause of parapatry and the restricted range of S. atra remain elusive. We combine multivariate approaches and climatic data analysis to explore niche differentiation among the two salamanders with respect to the available climatic environment at their contact zones. Our purpose is to evaluate whether climatic conditions explain the species’ sharp range limits or if biotic interactions may play a role for range delimitation. Analyses were carried out in three contact zones in Switzerland to assess possible geographic variation. Our results indicate that both species occur at localities with different climatic conditions as well as the presence of a strong climatic gradient across the species’ range limits. Although the species’ climatic niches differ moderately (with a wider niche breadth for S. atra), interspecific niche overlap is found. Comparisons among the contact zones confirm geographic variation in the species’ climatic niches as well as in the conditions within the geographically available space. Our results suggest that the change in climatic conditions along the recognized gradient represents a determining factor for species’ range limits within contact zones. However, our analyses of geographic variation in climatic conditions reveal that both salamander species can occur in a much wider range of conditions than observed within contact zones. This finding and the interspecific climatic niche overlap within each contact zone provides indirect evidence that biotic interactions (likely competition) between the two species may also determine their range limits.     

Niche overlap of mountain hare subspecies and the vulnerability of their ranges to invasion by the European hare; the (bad) luck of the Irish

Niche conservatism is the tendency of related species to retain ancestral tolerances after geographic separation. We used Ecological Niche Modelling and Principal Components Analysis of bioclimatic and habitat variables to describe the extent of the species niche, and degrees of bioclimatic–habitat niche conservatism within the mountain hare (L. timidus) clade. Mountain hare niche space was contrasted with that of the European hare (L. europaeus), to shed light on species interactions in contact zones throughout Europe. All five subspecies of mountain hare had quantifiably distinct niches. Fennoscandian (L.t. sylvaticus, L.t. timidus) and highland (L.t. scoticus, L.t. varronis) subspecies, however, were most similar, exhibiting greatest apparent niche conservatism. They inhabit tundra, boreal forest and uplands, and, hence are presumed most similar to the ancestral form. The Irish hare was distinct, being consistently distinguished from other mountain hares in both 2D and nth dimensional (4D) niche space. The ecological distinctiveness of the Irish hare provides further evidence that it is an Evolutionarily Significant Unit, particularly vulnerable to displacement by introduced European hares with which it competes and hybridises. Projections under global climate change suggest that, by 2070, bioclimatic space for invasive European hares in Ireland will expand (by 79%) but contract for endemic Irish hares (by 75%), further facilitating their replacement. The near complete species replacement of the heath hare (L.t. sylvaticus) in southern Sweden, where the European hare has also been introduced, may suggest a similar fate may be in store for the Irish hare.     

Geographic morphological variation in parapatric Western Palearctic tree frogs,Hyla arborea and Hyla savignyi: are related species similarly affected by climatic conditions?

Tree frogs Hyla arborea and Hyla savignyi are similar, closely‐related species distributed in Europe and the Middle East. We investigated geographic variation in body shape within and between these species, and tested its relationships to macroclimatic conditions. We used morphometric distances (based on size corrected external measurements) to construct phenetic trees (unweighted pair‐group method of arithmetical averages, Neighbour‐joining), and to test correlations between morphology, geography, and climate by the partial Mantel test. Regardless of their specific affiliation, the parapatric populations of both species from the eastern Mediterranean, where they occupy comparable habitats, are closer to each other in morphospace than to conspecific populations from distal regions. This local interspecific similarity is probably driven by the common response to environment, expressed here as macroclimatic conditions. In support, the geographically close but ecologically vicariant populations of both species from the Caucasus region differ quite substantially in body shape. We suggest that climate‐provoked phenotypic variation in closely‐related parapatric species should be taken into account as a potential complication to character displacement in morphology. Contrariwise, morphological diversification between related species or their populations could be enhanced by habitat shifts resulting in occupation of different environmental space. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 539–556.     

Analysis of MC1R genetic variation in Lepus species in Mediterranean refugia

A study on the inter- and intraspecies variation of MC1R gene was performed in Lepus species inhabiting the Mediterranean basin (L. granatansis, L. europaeus, L. corsicanus, L. castroviejoi and L. mediterraneus) and their neighboring species in Europe (L. timidus) and Africa (L. saxatilis, L. capensis), in order to infer micro- versus macroevolutionary adaptation. Eleven different sequences were isolated that corresponded to five amino acid sequences. Comparison of MC1R nucleotide phylogenetic tree with phylogenies resulting from mtDNA regions of the same species showed absence of congruence between these sets of markers. The Mediterranean area that offered refugia during last glaciation retains more MC1R genotypes compared with populations of North and Central Europe as a consequence of founder effects. L. corsicanus and L. castroviejoi bore identical alleles supportive of their conspecificity, as indicated by other molecular markers. Within L. europaeus, a group of Israeli hares were distinguished by a different MC1R functional allele; additional differences in coat colour and other genetic markers raise doubts about its taxonomic status. Finally, the present data reinforced the idea of bi-directional introgressive hybridization between L. europaeus and L. timidus in Switzerland.     

Genetic diversity in epichloid endophytes of Hordelymus europaeus suggests repeated host jumps and interspecific hybridizations

Epichloid fungal endophytes (Epichloë and Neotyphodium spp.) are excellent model systems for studying speciation processes because of their variable life history traits that are linked to host grass fitness. Presumed jumps to new hosts and subsequent somatic hybridizations appear to be common among epichloid endophytes resulting in increased genetic variation upon which selection can act and speciation be initiated. In this study, we explored the endophyte diversity of a rare European native woodland grass species, Hordelymus europaeus, along a latitudinal transect covering the entire distribution range of H. europaeus. From 28 populations in six countries, isolates were sampled and molecularly characterized. Based on the sequences of tubB and tefA, six distinct epichloid taxa (interspecific hybrid or cryptic haploid species) were found, of which four were novel and two have been previously reported from this host. Of the novel endophytes, two were presumed to be interspecific hybrids and two of nonhybrid origin. While previously known endophytes of H. europaeus are seed‐born and strictly asexual, one of the novel nonhybrid endophytes found in the glacial refugium of the Apennine peninsula reproduced sexually in cultured plants. This is the first case of a seed‐borne, but sexually reproducing endophyte of this host. We discuss the origin, and possible ancestral species, of the six epichloid taxa using phylogenetic analyses. Repeated host jumps and somatic hybridizations characterize the diversity of the endophytes. To date, no other grass species is known to host a larger diversity of endophytes than H. europaeus.     

The distribution of mountain hares Lepus timidus in Europe: a challenge from brown hares L. europaeus?

1. Throughout the most recent glacial period (Weichsel), the mountain hare Lepus timidus had a continuous distribution in the tundra habitat south of the ice‐rim. When the ice retreated, mountain hares colonized deglaciated land, and spread over northern Europe. 2. Since the Weichsel, the mountain hare's distribution in Europe has been gradually reduced and at present comprises Ireland and the Scottish Highlands, high altitudes in the Alps, isolated forests in eastern Poland, most of Fennoscandia and from the Baltic countries eastwards through Russia. Declines during the last century have been observed in Sweden and Russia. 3. This review defines and evaluates causes for this gradual reduction and fragmentation of the mountain hare's distribution, with special focus on interactions with brown hares Lepus europaeus. The relative importance of diseases, predation, cultivation and interactions with other herbivores than brown hares are discussed. 4. A plausible cause of the possible permanent disappearance of mountain hares in Europe appears to be exclusion by interspecific competition and hybridization with, and/or epidemic diseases mediated by, the congeneric brown hare.     

Ecological correlates of the distribution limits of two poeciliid species along a salinity gradient

Identifying the environmental factors responsible for the formation of a species' distribution limit is challenging because organisms interact in complex ways with their environments. However, the use of statistical niche models in combination with the analysis of phenotypic variation along environmental gradients can help to reduce such complexity and identify a subset of candidate factors. In the present study, we used such approaches to describe and identify factors responsible for the parapatric distribution of two closely‐related livebearer fish species along a salinity gradient in the lowlands of Trinidad, West Indies. The downstream distribution limits of Poecilia reticulata were strongly correlated with the brackish–freshwater interface. We did not observe significant phenotypic variation in life‐history traits for this species when comparing marginal with more central populations, suggesting that abrupt changes in conditions at the brackish–freshwater interface limit its distribution. By contrast, Poecilia picta was present across a wide range of salinities, although it gradually disappeared from upstream freshwater localities. In addition, P. picta populations exhibited an increase in offspring size in localities where they coexist with P. reticulata, suggesting a role for interspecific competition. The parapatric distribution of these two species, suggests that P. reticulata distributions are limited by an abiotic factor (salinity), whereas P. picta is limited by a biotic factor (interspecific competition). Similar parapatric patterns have been previously described in other systems, suggesting they might be a common pattern in nature. © 2013 The Linnean Society of London     

The importance of biotic interactions for modelling species distributions under climate change

Aim There is a debate as to whether biotic interactions exert a dominant role in governing species distributions at macroecological scales. The prevailing idea is that climate is the key limiting factor; thus models that use present‐day climate–species range relationships are expected to provide reasonable means to quantify the impacts of climate change on species distributions. However, there is little empirical evidence that biotic interactions would not constrain species distributions at macroecological scales. We examine this idea, for the first time, and provide tests for two null hypotheses: (H₀ 1) – biotic interactions do not exert a significant role in explaining current distributions of a particular species of butterfly (clouded Apollo, Parnassius mnemosyne) in Europe; and (H₀ 2) – biotic interactions do not exert a significant role in predictions of altered species’ ranges under climate change. Location Europe. Methods Generalized additive modelling (GAM) was used to investigate relationships between species and climate; species and host plants; and species and climate + host plants. Because models are sensitive to the variable selection strategies utilised, four alternative approaches were used: AIC (Akaike's Information Criterion), BIC (Bayesian Information Criterion), BRUTO (Adaptive Backfitting), and CROSS (Cross Selection). Results In spite of the variation in the variables selected with different methods, both hypotheses (H₀ 1 and H₀ 2) were falsified, providing support for the proposition that biotic interactions significantly affect both the explanatory and predictive power of bioclimatic envelope models at macro scales. Main conclusions Our results contradict the widely held view that the effects of biotic interactions on individual species distributions are not discernible at macroecological scales. Results are contingent on the species, type of interaction and methods considered, but they call for more stringent evidence in support of the idea that purely climate‐based modelling would be sufficient to quantify the impacts of climate change on species distributions.     

The phylogeny ofActaea (Ranunculaceae): A biogeographical approach

Phylogenetic analyses of the genusActaea were performed using morphological, ecological and biogeographical characters. Using solely morphological characters, the relationships of the three identified species-groups remain uncertain. Close biogeographical examination and comparison of the areas with ecological peculiarities as well as climate data gave important insight into the phylogeny ofActaea and the whole tribe. Consequently, the obtained biogeographical data were used for phylogenetic reconstructions. Both, from the point of view of morphological and biogeographical data,A. pachypoda andA. asiatica are the most ancestral species. They grow on the east sides of the continents, mainly in broad-leaved forests. In West Eurasia the apomorphicA. spicata andA. acuminata occur under similar climatic and ecological conditions, but these species are adapted to another climate rhythm. The most advanced species (A. erythrocarpa, A. rubra) are to be found in the boreal forests where they are widely distributed. This biogeographical approach revealed that the evolution of the species led to a gradual widening and shifting of their ecological constitutions.     

浙江江山公益林物种种间关系及CCA排序

利用浙江省江山市80个公益林固定小班监测数据,基于生态位理论、种间联结、CCA排序方法对研究区内群落优势种种间关系及其与环境的关系进行研究。结果表明:江山市公益林群落中杉木、檵木、紫萁分别在乔木、灌木、草本层中占优势地位;石栎与青冈、隔药柃与山苍子、蕨与海金沙的生态位重叠指数值分别在乔、灌、草本层中最大;而CCA协变量矩阵偏典范对应分析说明物种分布主要受海拔、坡度、坡向(光照强度)以及腐殖质厚度的影响,总体上可以对89.44%的环境因子进行解释。并且还表明,生态位宽度较大的物种其生态位重叠值较大,并在CCA排序图物种集中区分布。反之,生态位重叠较小,在CCA排序图中将偏离物种集中区;除此之外,在CCA排序图上,物种间的距离与其生态位重叠值的大小及种间联结均有密切的关联,若未存在显著的联结性,随物种间的生态位重叠值越高,其在CCA排序上的距离越近,若存在显著联结性,则正相关缩小距离,负相关拉大距离。