Pituophis ruthveni

Number of Pages: 16Geological SciencesIntegrative Biolog

Ecological correlates of risk and incidence of West Nile virus in the United States

West Nile virus, which was recently introduced to North America, is a mosquito-borne pathogen that infects a wide range of vertebrate hosts, including humans. Several species of birds appear to be the primary reservoir hosts, whereas other bird species, as well as other vertebrate species, can be infected but are less competent reservoirs. One hypothesis regarding the transmission dynamics of West Nile virus suggests that high bird diversity reduces West Nile virus transmission because mosquito blood-meals are distributed across a wide range of bird species, many of which have low reservoir competence. One mechanism by which this hypothesis can operate is that high-diversity bird communities might have lower community-competence, defined as the sum of the product of each species’ abundance and its reservoir competence index value. Additional hypotheses posit that West Nile virus transmission will be reduced when either: (1) abundance of mosquito vectors is low; or (2) human population density is low. We assessed these hypotheses at two spatial scales: a regional scale near Saint Louis, MO, and a national scale (continental USA). We found that prevalence of West Nile virus infection in mosquito vectors and in humans increased with decreasing bird diversity and with increasing reservoir competence of the bird community. Our results suggest that conservation of avian diversity might help ameliorate the current West Nile virus epidemic in the USA

Data from: Resident-invader phylogenetic relatedness, not resident phylogenetic diversity, controls community invasibility

A central goal of invasion biology is to elucidate mechanisms regulating community invasibility. Darwin’s naturalization hypothesis, one of the oldest hypotheses in invasion biology, emphasizes the importance of phylogenetic relatedness (PR) between resident and invader species for predicting invasibility. Alternatively, a recent extension of the diversity-invasibility hypothesis predicts that phylogenetic diversity (PD) of resident communities influences invasibility. Neither of these hypotheses has undergone rigorous experimental testing, and the relative contributions of PR and PD, whose effects tend to be confounded with each other, to community invasibility are unknown. Here we consider both perspectives together by independently manipulating PR and PD in laboratory bacterial assemblages. We found that while invader abundance declined significantly as PR increased, it was unaffected by PD. Likewise, we found that resident-invader functional similarity, not functional diversity of resident communities, was a significant predictor of invader abundance. Nevertheless, invader abundance was better predicted by PR than functional similarity. These results highlight the importance of considering species evolutionary relationships, especially the phylogenetic relatedness between resident and invader species, for the prediction, prevention and management of biological invasions

FRAGMENTATION ALTERS HOME RANGE AND MOVEMENTS OF THE DUNES SAGEBRUSH LIZARD (SCELOPORUS ARENICOLUS)

Habitat fragmentation is a major driver of biodiversity loss and among reptiles has been attributed as a cause of species decline. The negative effect of habitat fragmentation has also been shown to be worse for species that are habitat specialists. The Dunes Sagebrush Lizard (Sceloporus arenicolus Degenhardt and Jones 1972) is a species that specializes on the Shinnery Oak sand dune landform of the Mescalero-Monahans Sandhills ecosystem in western Texas and eastern New Mexico, USA. This landform has been fragmented by roads and well pads used for the extraction of oil and gas resources. The effects of fragmentation on the home range and movements of this species can lead to the effective isolation of populations and increased risk of localized extirpations. We showed that home range size was larger in an unfragmented area and that the average distance of movements was greater. We also observed that roads in the fragmented areas restricted movements of S. arenicolus. We concluded that roads can be barriers to movements even though only narrow strips of habitat are altered.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Landscape Pattern Determines Neighborhood Size and Structure within a Lizard Population

<div><p>Although defining population structure according to discrete habitat patches is convenient for metapopulation theories, taking this approach may overlook structure within populations continuously distributed across landscapes. For example, landscape features within habitat patches direct the movement of organisms and define the density distribution of individuals, which can generate spatial structure and localized dynamics within populations as well as among them. Here, we use the neighborhood concept, which describes population structure relative to the scale of individual movements, to illustrate how localized dynamics within a population of lizards (<i>Sceloporus arenicolus</i>) arise in response to variation in landscape pattern within a continuous habitat patch. Our results emphasize links between individual movements at small scales and the emergence of spatial structure within populations which resembles metapopulation dynamics at larger scales. We conclude that population dynamics viewed in a landscape context must consider the explicit distribution and movement of individuals within continuous habitat as well as among habitat patches.</p> </div

Site specific model estimates of local population size (<i>N</i>) followed by estimated density per 100 m² for <i>S. arenicolus</i> across 6 sites.

<p>Also shown are the standard error (SE) and confidence interval (95% CI).</p

Neighborhood recruitment and diffusion.

<p>(A) Larger neighborhood sizes maintained significantly higher recruitment rates (R² = 0.82, df = 4, P = 0.05; bars = ±SE), and (B) higher recruitment rates generated higher diffusion rates (R² = 0.80, df = 4, P = 0.05). Dashed lines estimate the threshold levels of recruitment, 0.13 (vertical), and diffusion rate, 5,625 m² (horizontal) required to balance population losses across sites and occupy the same area in the landscape (i.e., spatial equilibrium). Sites found above both thresholds (upper right) are identified as sources; the site found below both thresholds (lower left) is identified as a sink (see text).</p