Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species

Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene flow.Signatures of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales.

Climate and land-use interactively shape butterfly diversity in tropical rainforest and savanna ecosystems of southwestern China

Human-induced habitat conversion and degradation,along with accelerating climatic change,have resulted in considerable global biodiversity loss.Nevertheless,how local ecological assemblages respond to the interplay between climate and land-use change remains poorly understood.Here,we examined the effects of climate and land-use interactions on butterfly diversity in different ecosystems of southwestern China.Specifically,we investigated variation in the alpha and beta diversities of butterflies in different landscapes along human-modified and climate gradients.We found that increasing land-use intensity not only caused a dramatic decrease in butterfly alpha diversity but also significantly simplified butterfly species composition in tropical rainforest and savanna ecosystems.These findings suggest that habitat modification by agricultural activities increases the importance of deterministic processes and leads to biotic homogenization.The land-use intensity model best explained species richness variation in the tropical rainforest,whereas the climate and land-use intensity interaction model best explained species richness variation in the savanna.These results indicate that climate modulates the effects of land-use intensity on butterfly alpha diversity in the savanna ecosystem.We also found that the response of species composition to climate varied between sites:specifically,species composition was strongly correlated with climatic distance in the tropical rainforest but not in the savanna.Taken together,our long-term butterfly monitoring data reveal that interactions between human-modified habitat change and climate change have shaped butterfly diversity in tropical rainforest and savanna.These findings also have important implications for biodiversity conservation under the current era of rapid human-induced habitat loss and climate change.

Complementary fruiting phenologies facilitate sharing of one pollinator fig wasp by two fig trees

Aims most pollinator fig wasps are host plant specific,with each spe-cies only breeding in the figs of one fig tree species,but increasing numbers of species are known to be pollinated by more than one fig wasp,and in rare instances host switching can result in Ficus species sharing pollinators.in this study,we examined factors facilitating observed host switching at Xishuangbanna in southwestern(sW)China,where Ficus squamosa is at the northern edge of its range and lacks the fig wasps that pollinate it elsewhere,and its figs are colonized by a Ceratosolen pollinator that routinely breeds in figs of F.heterostyla.Methods We recorded the habitat preferences of F.squamosa and F.heterost-yla at Xishuangbanna,and compared characteristics such as fig size,location and colour at receptive phase.Furthermore,the vegetative and reproductive phenologies in the populations of F.squamosa and F.heterostyla were recorded weekly at Xishuangbanna Tropical botanical garden for 1 year.Important Findings Ficus squamosa is a shrub found near fast-flowing rivers,F.heterostyla is a small tree of disturbed forest edges.although preferring different habitats,they can be found growing close together.both species have figs located at or near ground level,but they differ in size when pollinated.Fig production in F.squamosa was concentrated in the colder months.F.heterostyla produced more figs in summer but had some through-out the year.The absence of its normal pollinators,in combination with similarly located figs and partially complementary fruiting patterns appear to have facilitated colonization of F.squamosa by the routine pollinator of F.heterostyla.The figs probably also share similar attractant volatiles.This host switching suggests one mechanism whereby fig trees can acquire new pollinators and emphasizes the likely significance of edges of ranges in the genesis of novel fig tree-fig wasp relationships.

Diversity begets diversity:Low resource heterogeneity reduces the diversity of nut-nesting ants in rubber plantations

One of the most general patterns in ecology is the positive relationship between environmental heterogeneity and local diversity.On the one hand,increased resource heterogeneity provides more resources for diverse consumers in the community.On the other hand,increased structural heterogeneity creates variation in the environment’s physical structure,thus allowing the coexistence of diverse species with different environmental requirements.Here,we examined the relative importance of resource and structural heterogeneity in determining the taxonomic,functional,and phylogenetic diversity of nutnesting ants in natural rainforest and rubber plantation.The species richness of nut-nesting ants was 70%higher in rainforest than in rubber plantation.The clustered functional and phylogenetic structure in rubber plantation suggested a strong effect of environmental filtering in shaping ant functional and phylogenetic structure.Nesting heterogeneity(nut diversity)was the major factor explaining variation in taxonomic,functional,and phylogenetic diversity,suggesting that resource heterogeneity plays a major role in shaping the biodiversity patterns of nut-nesting ants.Overall,these results indicate that decreased resource diversity following the conversion of rainforest to rubber plantation can drive biodiversity loss in nut-nesting ants,through its effect on reducing both ant species,functional,and phylogenetic diversity.The decline in species richness and functional and phylogenetic diversity in the local ant community might have major effects on ecosystem functioning.

Disturbance effects on community structure of Ficus tinctoria fig wasps in Xishuangbanna, China： Implications for the fig/fig wasp mutualism

Fig trees are important components of tropical forests, because their fruits are eaten by so many vertebrates, but they depend on pollinating fig wasps to produce mature fruits. Disturbance to habitat structure can have a major impact on insect diversity and com- position, potentially reducing fruit yields. We investigated the impact of habitat disturbance on the fig wasp community associated with male figs ofFicus tinctoria in Xishuangbanna, China. The community comprised one pollinator species Liporrhopalum gibbosae and six non-pollinating wasp species： Sycoscapter sp. 1, Philotrypesis ravii, Philotrypesis sp. 1, Neosycophila omeomorpha, Sycophila sp.1, and Walkerella sp.1. More disturbed areas were characterized by higher temperatures, less shade, and more vehicle noise. The response of the fig wasp community was complex, with no simple relationship between intensity of disturbance and pollinator abundance. However, the sex ratios （proportion of male progeny） of pollinators increased significantly in more disturbed areas. We conclude that potential changes in fig wasp community composition brought about by disturbance, are unpredictable, with unclear consequences for tropical rainforest biodiversity.