Comparative phylogeography of two co‐distributed but ecologically distinct rainbowfishes of far‐northern Australia

Aim

To test the influence of historical and contemporary environment in shaping the genetic diversity of freshwater fauna we contrast genetic structure in two co‐distributed, but ecologically distinct, rainbowfish; a habitat generalist (Melanotaenia splendida) and a habitat specialist (M. trifasciata).

Location

Fishes were sampled from far northern Australia (Queensland and Northern Territory).

Methods

We used sequence data from one mitochondrial gene and one nuclear gene to investigate patterns of genetic diversity in M. splendida and M. trifasciata to determine how differences in habitat preference and historical changes in drainage boundaries affected patterns of connectivity.

Results

Melanotaenia splendida showed high levels of genetic diversity and little population structure across its range. In contrast, M. trifasciata showed high levels of population structure. Whereas phylogeographic patterns differed, both species showed a strong relationship between geographical distance and genetic differentiation between populations. Melanotaenia splendida showed a shallower relationship with geographical distance, and genetic differentiation was best explained by stream length and a lower scaled ocean distance (11.98 times coast length). For M. trifasciata, genetic differentiation was best explained by overwater distance between catchments and ocean distance scaled at 1.16 × 10⁶ times coast length.

Main conclusions

Connectivity of freshwater populations inhabiting regions periodically interconnected during glacial periods appears to have been affected by ecological differences between species. Species‐specific differences are epitomized here by the contrast between co‐distributed congeners with different habitat requirements: for the habitat generalist, M. splendida, there was evidence for greater historical genetic connectivity with oceans as a weaker barrier to gene exchange in contrast with the habitat specialist, M. trifasciata.     

Individual tree context and contrast dictate tree physiological features and arthropod biodiversity patterns across multiple trophic levels

1. The present study tested the hypothesis that tree context (natural, semi-natural or planted) and contrast (height of surrounding vegetation) affect tree physiological characters (leaf size, nutrient content, and stress-related factors), and also alter the arthropod biodiversity patterns either directly or indirectly. 2. Arthropods were collected from tree canopies using chemical fogging from the ecologically important South African native tree Podocarpus elongatus. 3. Low contrast trees had significantly larger leaves than those in high contrast environments and harboured an overall higher richness, abundance, and biomass of arthropods, although this was guild-dependent. 4. Trees in natural contexts had less foliar δ¹³C, suffered less from artificial nitrogen enrichment, and harboured significantly higher herbivore and predator arthropod richness and unique assemblages, compared with planted trees. 5. Semi-natural trees supported natural levels of arthropod richness, although these were mostly generalist species. 6. Tree context and contrast can therefore dictate associated biota at multiple trophic levels and native trees may fail to maintain natural biodiversity in transformed landscapes.     

Gene expression kinetics in individual plasmodial cells reveal alternative programs of differential regulation during commitment and differentiation

During its life cycle, the amoebozoon Physarum polycephalum forms multinucleate plasmodial cells that can grow to macroscopic size while maintaining a naturally synchronous population of nuclei. Sporulation‐competent plasmodia were stimulated through photoactivation of the phytochrome photoreceptor and the expression of sporulation marker genes was analyzed quantitatively by repeatedly taking samples of the same plasmodial cell at successive time points after the stimulus pulse. Principal component analysis of the gene expression data revealed that plasmodial cells take different trajectories leading to cell fate decision and differentiation and suggested that averaging over individual cells is inappropriate. Queries for genes with pairwise correlated expression kinetics revealed qualitatively different patterns of co‐regulation, indicating that alternative programs of differential regulation are operational in individual plasmodial cells. At the single cell level, the response to stimulation of a non‐sporulating mutant was qualitatively different as compared to the wild type with respect to the differentially regulated genes and their patterns of co‐regulation. The observation of individual differences during commitment and differentiation supports the concept of a Waddington‐type quasipotential landscape for the regulatory control of cell differentiation. Comparison of wild type and sporulation mutant data further supports the idea that mutations may impact the topology of this landscape.     

基于MSPA-连接度-空间句法的生态保护空间及优先级识别——以苏锡常地区为例

随着城市化进程的加快,对生态保护空间(Ecological Protect Area,EPA)进行优先级识别已经成为保护生物多样性,缓解城市生态压力,提高土地利用效率的重要方法之一。以苏锡常地区为例,通过形态空间格局分析(Morphological Spatial Pattern Analysis,MSPA)确定EPA,进而采用景观连接度方法对其优先级进行识别,以优先级较高的林地和水域为"源地",构建EPA网络;同时由于景观连接度方法在识别优先级时,未能体现EPA对物种决策的非等权重影响,因此本研究引入空间句法进一步对EPA进行优先级识别。结果显示:1)苏锡常地区EPA中编号1、2的林地以及太湖的优先级最高,是区域网络的3个中心,需要优先保护;2)引入空间句法的优先级识别结果与基于景观连接度的优先级识别结果存在明显差异,后者优先级较高的8个EPA,在引入空间句法后优先级降低1—2个等级;后者优先级较低的4个EPA的优先级则上升了2个等级。同时也表明:基于连接度-空间句法的EPA优先级识别方法能够反映不同景观要素对物种决策行为的非等权重影响,强化了生态要素的空间配置的生态效应,为明确关键性生态空间,提供了有效的方法补充,对保护生物多样性和维系区域生态安全具有重要意义。     

Bird communities in traditional wood-pastures with changing management in Eastern Europe

Wood-pastures are fragile ecosystems because they were formed by, and depend on specific, low-intensity multifunctional management. Although their ecological and cultural significance is high, wood-pastures are rapidly deteriorating all over Europe, mainly due to changing land use. We still lack a basic understanding of the ecological value of wood-pastures, and in which features they differ from other landscape elements. In this paper we investigated the ecological value of wood-pastures for passerine birds by (i) comparing bird assemblages of wood-pastures with those of closed forests and open pastures and (ii) exploring the relationships between variables describing wood-pastures and species traits of the bird assemblages. Our study region (Southern Transylvania, Romania) provides a unique opportunity to understand the importance of a traditional cultural and ecological environment for many different organisms. Wood-pastures had a higher overall number of bird species, and a higher spatial turnover in bird community composition than closed forests and open pastures. We found significant associations between bird species traits and habitat structural elements in wood-pastures such as large trees, oak- and pear trees and shrubs. Our findings suggest that traditional wood-pastures in Southern Transylvania have distinct and rich passerine bird communities. This richness is inextricably linked to the multifunctional, low-intensity land use traditionally applied in the wood-pastures that promotes high niche diversity. For effective conservation of the biodiversity of wood-pastures, a detailed understanding is needed of how different management regimes may influence the key structural elements of wood-pastures relevant for biodiversity and these should be protected.     

Northern bobwhite response to Conservation Reserve Program habitat and landscape attributes

The northern bobwhite (Colinus virginianus; hereafter bobwhite) has experienced substantial population declines in recent decades in the United States, and especially in Maryland and Delaware. The United States Department of Agriculture's Conservation Reserve Program (CRP) could provide additional habitat for bobwhites, leading to an increase in bobwhite abundance. I investigated if bobwhite abundance was related to the percent cover of CRP land and landscape attributes in local landscapes on Maryland's Eastern Shore and Delaware. Observers conducted bobwhite point transect surveys at 113 locations during the breeding seasons of 2006–2007, and I calculated landscape metrics for 500-m radius landscapes centered on each point transect location. Most CRP land in the study landscapes was planted to herbaceous vegetation. Bobwhite abundance was strongly positively associated with percent cover of CRP land in the landscape but was not strongly related to percent cover of agriculture or forest or to landscape patch density. These results suggest that the CRP has created additional habitat for bobwhites in Maryland and Delaware and that landscapes with greater proportions of herbaceous CRP practices support more bobwhites. © 2012 The Wildlife Society.     

Fine‐scale variation within urban landscapes affects marking patterns and gastrointestinal parasite diversity in red foxes

1. Urban areas are often considered to be a hostile environment for wildlife as they are highly fragmented and frequently disturbed. However, these same habitats can contain abundant resources, while lacking many common competitors and predators. The urban environment can have a direct impact on the species living there but can also have indirect effects on their parasites and pathogens. To date, relatively few studies have measured how fine‐scale spatial heterogeneity within urban landscapes can affect parasite transmission and persistence.
2. Here, we surveyed 237 greenspaces across the urban environment of Edinburgh (UK) to investigate how fine‐scale variation in socio‐economic and ecological variables can affect red fox (Vulpes vulpes) marking behavior, gastrointestinal (GI) parasite prevalence, and parasite community diversity.
3. We found that the presence and abundance of red fox fecal markings were nonuniformly distributed across greenspaces and instead were dependent on the ecological characteristics of a site. Specifically, common foraging areas were left largely unmarked, which indicates that suitable resting and denning sites may be limiting factor in urban environments. In addition, the amount of greenspace around each site was positively correlated with overall GI parasite prevalence, species richness, and diversity, highlighting the importance of greenspace (a commonly used measure of landscape connectivity) in determining the composition of the parasite community in urban areas.
4. Our results suggest that fine‐scale variation within urban environments can be important for understanding the ecology of infectious diseases in urban wildlife and could have wider implication for the management of urban carnivores.