Ecography最新文献

Himalayan orogeny and consequent climatic changes, such as the strengthening of the Asian monsoon, are considered as two main drivers in shaping local biogeography. The mountainous Sinopoda spiders, which are widely distributed in East Asia and Southeast Asia and especially abundant in the mountains near the Himalayas, represent an ideal model lineage for investigating Himalayan biogeography. This is due to their high diversity, limited dispersal ability, and wide elevational distribution, ranging from sea level up to 3500 meters. We investigated the evolutionary history of Sinopoda spiders, focusing on ecological, molecular, and morphological traits in relation to local geological events and fluctuations in Neogene (23.0–2.6 Ma) Asian monsoon patterns. Distribution modeling results show that extant Sinopoda spiders are sensitive to humidity fluctuations. They are mainly distributed in two distinct habitats: areas with moderate precipitation at high altitude (relatively cold) and areas with high precipitation at low altitude (relatively warm). The biogeographical and elevation reconstruction analyses show that as the Himalayas rose and the Asian monsoon intensified, Sinopoda spiders (Sparassidae: Heteropodinae) moved out of the Himalayas (ca 18.1 Ma) then ‘down' the rising mountain slopes (ca 9.6 Ma). We then see a secondary return to the mountains (ca 3.3 Ma) as the severity of the East Asian monsoon decreased. We hypothesize that our ‘out of Himalaya' dispersal pattern hypothesis will also apply to closely related spider groups with limited ballooning ability (e.g. Lycosidae, Thomisidae) or other organisms with low vagility (such as herpetofauna) that are sensitive to humidity and possess similar geographical distributions.

The relative importance of the different processes that determine the distribution of species and the assembly of communities is a key question in ecology. The distribution of any individual species is affected by a wide range of environmental variables as well as through interactions with other species; the resulting distributions determine the pool of species available to form local communities at fine spatial scales. A challenge in community ecology is that these interactions (e.g. competition, facilitation, etc.) often are not directly measurable. Here, we used hierarchical modelling of species communities (HMSC), a recently developed framework for joint species distribution modelling, to estimate the role of biotic effects alongside environmental factors using latent variables. We investigate the role of these factors determining species distributions in communities of Artiodactyla, Perissodactyla and Proboscidea in the Afrotropics, an area of peak species richness for hoofed mammals. We also calculate pairwise trait dissimilarity between these species, from a mixture of morphological and behavioural traits, and investigate the relationship between dissimilarity and estimated residual co-occurrence in the model. We find that while ungulate distributions appear to be predominantly determined (~ 70%) by climatic variables, such as precipitation, a substantial proportion of the variance in ungulate species distributions (~ 30%) can also be attributed to modelled latent variables that likely represent a combination of dispersal barriers and biotic factors. Although we find only a weak relationship between residual co-occurrence and trait dissimilarity, we suggest that our results may show evidence that biotic factors, likely influenced by historical barriers to species dispersal, are important in determining species communities over a continental area. The HMSC framework can be used to provide insight into factors affecting community assembly at broad scales, and to make more powerful predictions about future species distributions as we enter an era of increasing impacts from anthropogenic change.

While much attention has been paid to the climatic controls of species' range limits, other factors such as dispersal limitation are also important. Temperature is an important control of the distribution of coastal mangrove forests, and mangrove expansion at multiple poleward range limits has been linked to increasing temperatures. However, mangrove abundances at other poleward range limits have been surprisingly insensitive to climate change, indicating other drivers of range limitation. For example, along the west coast of North America, the poleward mangrove range limits are found on the Baja California and mainland coasts of Mexico, between 26°48ʹ and 30°18ʹN. Non-climatic factors may play an important role in setting these range limits as 1) the abundance of range limit populations has been relatively insensitive to climate variability and 2) an introduced population of mangroves has persisted hundreds of kilometers north of the natural range limits. We combined a species distribution model with a high-resolution oceanographic transport model to identify the roles of climate and dispersal limitation in controlling mangrove distributions. We identified estuarine habitat that is likely climatically suitable for mangroves north of the current range limits. However, propagules from current mangrove populations are unlikely to reach these suitable locations due to prevailing ocean currents and geomorphic factors that create a patchy distribution of estuarine habitat with large between-patch distances. Thus, although climate change is driving range shifts of mangroves in multiple regions around the world, dispersal is currently limiting poleward mangrove expansion at several range limits, including the west coast of North America.