Are plant hybrid zones centers of vertebrate biodiversity? A test in the Quercus grisea × Quercus gambelii species complex

The plant-hybrid-zones-as-centers-of-biodiversity (hereafter, PHZCB) hypothesis posits that plant hybrid zones represent areas of elevated biodiversity, and supports the inclusion of plant hybrid zones in conservation efforts. Support for the PHZCB hypothesis is limited to a handful of cases involving insect and fungal species and to two studies involving higher trophic levels. The PHZCB hypothesis requires further testing before plant hybrid zones can be established with any certainty as centers of biodiversity. We test whether the PHZCB hypothesis holds for higher trophic levels by examining the community structure of birds and reptiles associated with the Quercus grisea × Quercus gambelii species complex. Specifically, we compare patterns of species richness and abundance of these taxa in 10 hybrid zones and 11 contact zones (i.e., zones where both parental species occur but hybrids do not). In contrast to predictions of the PHZCB hypothesis, contact zones supported significantly more species of birds and reptiles than did hybrid zones. Species abundances exhibited idiosyncratic responses to zone type, but were higher generally in the contact zones.     

Response of vegetation and vertebrate fauna to 23 years of fire exclusion in a tropical Eucalyptus open forest,Northern Territory,Australia

Abstract This opportunistic study compares the vegetation, fuel loads and vertebrate fauna of part of a 120‐ha block of tropical open forest protected from fire for 23 years, and an adjacent block burnt annually over this period. Total fuel loads did not differ significantly between the unburnt and annually burnt sites, but their composition was markedly different, with far less grassy fuel, but far more litter fuel, in the unburnt block. There were major differences between treatments in the composition of trees and shrubs, manifest particularly in the number of stems. There was no overall difference in plant species richness between the two treatments, but richness of woody species was far higher in the unburnt treatment, and of annual and perennial grasses, and perennial herbs in the annually burnt treatment. Change in plant species composition from annually burnt to unburnt treatment was directional, in that there was a far higher representation of rainforest‐associated species (with the percentage of woody stems attributable to ‘rainforest’ species increasing from 24% of all species in the annually burnt treatment to 43% in the unburnt treatment, that of basal area from 9% to 30%, that of species richness from 8% to 17%, and that of cover from 12 to 47%). The vertebrate species composition varied significantly between treatments, but there was relatively little difference in species richness (other than for a slightly richer reptile fauna in the unburnt treatment). Again, there was a tendency for species that were more common in the unburnt treatment to be rainforest‐associated species. The results from this study suggest that there is a sizeable and distinct set of species that are associated with relatively long‐unburnt environments, and hence that are strongly disadvantaged under contemporary fire regimes. We suggest that such species need to be better accommodated by fire management through strategic reductions in the frequency of burning.     

四川美姑大风顶自然保护区两栖爬行动物资源调查

20 0 2年 8月 1日～ 17日对四川美姑大风顶自然保护区的两栖爬行动物进行了调查。结合前人的工作 ,该保护区共有两栖爬行动物 2 2种 ,其中两栖动物 11种 ,隶属于 9属 7科 2目 ,爬行动物 11种 ,隶属于 9属 4科 2亚目 1目。区系特点为 :(1)物种组成较丰富 ;(2 )都属于东洋界物种 ,没有古北界的成分 ;(3)区系组成较简单 ,以喜马控雅 -横断山区型和南中国型为主 ;(4 )特有种所占比例高。 (5 )既古老又具年轻的特点。美姑县新纪录 6种 ,大凉疣螈为国家Ⅱ级重点保护野生动物 ,横斑锦蛇为四川省重点保护野生动物。美姑大风顶自然保护区两栖爬行动物物种多样性和生境多样性较高 ,对于生物多样性保护和研究横断山脉两栖爬行动物物种组成及区系特征具有一定意义。     

A comparison of methods for mapping species ranges and species richness

Aim  Maps of species richness are the basis for applied research and conservation planning as well as for theoretical research investigating patterns of richness and the processes shaping these patterns. The method used to create a richness map could influence the results of such studies, but differences between these methods have been insufficiently evaluated. We investigate how different methods of mapping species ranges can influence patterns of richness, at three spatial resolutions.
Location  California, USA.
Methods  We created richness maps by overlaying individual species range maps for terrestrial amphibians and reptiles. The methods we used to create ranges included: point-to-grid maps, obtained by overlaying point observations of species occurrences with a grid and determining presence or absence for each cell; expert-drawn maps; and maps obtained through species distribution modelling. We also used a hybrid method that incorporated data from all three methods. We assessed the correlation and similarity of the spatial patterns of richness maps created with each of these four methods at three different resolutions.
Results  Richness maps created with different methods were more correlated at lower spatial resolutions than at higher resolutions. At all resolutions, point-to-grid richness maps estimated the lowest species richness and those derived from species distribution models the highest. Expert-drawn maps and hybrid maps showed intermediate levels of richness but had different spatial patterns of species richness from those derived with the other methods.
Main conclusions  Even in relatively well-studied areas such as California, different data sources can lead to rather dissimilar maps of species richness. Evaluating the strengths and weaknesses of different methods for creating a richness map can provide guidance for selecting the approach that is most appropriate for a given application and region.     

Predicting reptile distributions at the mesoscale: relation to climate and topography

Aim To explore the respective power of climate and topography to predict the distribution of reptiles in Switzerland, hence at a mesoscale level. A more detailed knowledge of these relationships, in combination with maps of the potential distribution derived from the models, is a valuable contribution to the design of conservation strategies. Location All of Switzerland. Methods Generalized linear models are used to derive predictive habitat distribution models from eco‐geographical predictors in a geographical information system, using species data from a field survey conducted between 1980 and 1999. Results The maximum amount of deviance explained by climatic models is 65%, and 50% by topographical models. Low values were obtained with both sets of predictors for three species that are widely distributed in all parts of the country (Anguis fragilis, Coronella austriaca, and Natrix natrix), a result that suggests that including other important predictors, such as resources, should improve the models in further studies. With respect to topographical predictors, low values were also obtained for two species where we anticipated a strong response to aspect and slope, Podarcis muralis and Vipera aspis. Main conclusions Overall, both models and maps derived from climatic predictors more closely match the actual reptile distributions than those based on topography. These results suggest that the distributional limits of reptile species with a restricted range in Switzerland are largely set by climatic, predominantly temperature‐related, factors.     

Comparative study of the corneal epithelium in some reptiles inhabiting different environments

El‐Bakry, A.M. 2011. Comparative study of the corneal epithelium in some reptiles inhabiting different environments. —Acta Zoologica (Stockholm) 92 : 54–61. The vertebrate cornea functions in either aquatic or aerial environments and in some cases in both. In terrestrial and aerial vertebrates, the cornea contributes most of the refractive powers of the eye because of the large variation in refractive index between the air and the cornea. The present study aimed to examine and compare the main features of the corneal epithelial surface of three reptilian species related to three different families (Caretta caretta, Varanus griseus and Mabuya quinquetaeniata) and inhabiting different environment, by light, scanning (SEM) and transmission electron microscopy. The mean epithelial cell densities of the species of the study were 8.670 ± 3.134, 5.945 ± 2.144 and 2.124 ± 713 respectively. The corneal epithelium of the three species observed by SEM showed a similarity to one another indicating that the apical cell surfaces possess regular polygonal cells with varieties of microprocesses. These microprocesses were represented by microplicae, numerous microvilli and some long microridges in C. caretta, microplicae and minute microholes in V. griseus and microplicae intermingled with short microvilli in M. quinquetaeniata. According to the densities of these microprocesses, three polymorphic cell types (light, medium and dark) appeared in C. caretta, light and medium cell types were observed in V. griseus and medium and dark cell types were noticed in M. quinquetaeniata. Different types of tight adhesions were observed by transmission electron microscopy between the cell borders of the epithelial cells which differ according to environment where the species occupy. In conclusion, variation in the structure of the corneal epithelial cells appears to be related to the living environment, such as aerial, terrestrial and aquatic ones, which is occupied by every species.     

Histological study and immunohistochemical location of cytoskeletal proteins in the testis and epididymis of the three species of lizards of the family Leiosauridae (Reptilia: Squamata)

The objective of the study was to histologically describe the structure of the testis and epididymis, identifying the GAGs in them. Furthermore, the distribution of smooth muscle alpha-actin, desmin, and vimentin is described of E. bilineatus, E. perditus, and U. vautieri, through immunohistochemical method. Two adult males of each species of the lizards were collected in southeastern Brazil. In the testicular albuginea, the presence of neutral glycoproteins was detected. In E. bilineatus, the epididymal duct epithelium is simple, composed of secretory cells, cylindrical in shape and acidophilic cytoplasm. In the testis of the three lizards there was a positive immunolocation accentuated for α-SMA in the dense connective tissue of the tunica albuginea. A moderate reaction was observed in the connective tissue albuginous and in the layer of smooth muscle fibers in a circumferential arrangement of the epididymal duct. The immunolocation for desmin was accentuated in the fibers of the testicular albuginea of E. bilineatus, while in U. vautier and E. perditus was moderate. In the epididymis, only in E. perditus and E. bilineatus positive immunoreaction was verified. In the three lizards there were no observations of immunostaining for vimentin with the antibody utilized.     

Sexual signal evolution and patterns of assortative mating across an intraspecific contact zone

Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red-eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A. callidryas differ in a number of traits, several of which are known sexual signals that mediate premating reproductive isolation in allopatric populations. Along the Caribbean coast of Costa Rica, a ~100 km contact zone, situated between two phenotypically and genetically divergent parent populations, contains multiple colour pattern phenotypes and late-generation hybrids. This contact zone provides the opportunity to examine processes that are important in the earliest stages of lineage divergence. We performed analyses of colour pattern variation in five contact zone sites and six parental sites and found complex, continuous colour variation along the contact zone. We found discordance between the geographic distribution of colour pattern and previously described genomic population structure. We then used a parental site and contact zone site to measure assortative mating and directional selection from naturally-occurring amplectant mating pairs. We found assortative mating in a parental population, but no assortative mating in the contact zone. Furthermore, we uncovered evidence of directional preference towards the adjacent parental phenotype in the contact zone population, but no directional preference in the parent population. Combined, these data provide insights into potential dynamics at the contact zone borders and indicate that incipient speciation between parent populations will be slowed.