Functional differences between summer and winter season rain assessed with MODIS‐derived phenology in a semi‐arid region

Questions: We asked several linked questions about phenology and precipitation relationships at local, landscape, and regional spatial scales within individual seasons, between seasons, and between year temporal scales. (1) How do winter and summer phenological patterns vary in response to total seasonal rainfall? (2) How are phenological rates affected by the previous season rainfall? (3) How does phenological variability differ at landscape and regional spatial scales and at season and inter‐annual temporal scales? Location: Southern Arizona, USA. Methods: We compared satellite‐derived phenological variation between 38 distinct 625‐km² landscapes distributed in the northern Sonoran Desert region from 2000 to 2007. Regression analyses were used to identify relationships between landscape phenology dynamics in response to precipitation variability across multiple spatial and temporal scales. Results: While both summer and winter seasons show increases of peak greenness and peak growth with more precipitation, the timing of peak growth was advanced with more precipitation in winter, while the timing of peak greenness was advanced with more precipitation in summer. Surprisingly, summer maximum growth was negatively affected by winter precipitation. The spatial variations between summer and winter phenology were similar in magnitude and response. Larger‐scale spatial and temporal variation showed strong differences in precipitation patterns; however the magnitudes of phenological spatial variability in these two seasons were similar. Conclusions: Vegetation patterns were clearly coupled to precipitation variability, with distinct responses at alternative spatial and temporal scales. Disaggregating vegetation into phenological variation, spanning value, timing, and integrated components revealed substantial complexity in precipitation‐phenological relationships.     

Age distribution of lactating New Zealand sea lions: Interannual and intersite variation

The age distribution of 865 lactating New Zealand sea lions (NZSLs; Phocarctos hookeri ) was investigated over 3 yr (1999–2001) at two breeding colonies, Sandy Bay and Dundas Island, New Zealand. Lactating females were aged between 3 and 26 yr with a maximum observed age of 28 yr. The mean age of lactating females was 11.1 (SE = 0.16) yr. Age distributions peaked at ages 8 and 9 with a strong skew toward younger females, likely indicative of maximum recruitment into the breeding population by this age. There were significant intersite differences in age structure and also significant interannual differences in age distributions at Sandy Bay, but not at Dundas Island. Given that the two colonies are less than 10 km apart, have some interchange, and share foraging areas, these differences are surprising. However, the colony at Dundas Island is almost four times larger than Sandy Bay and may therefore be less sensitive to demographic or environmental stochasticity. That age distributions of NZSLs vary significantly over small temporal and spatial scales has important implications for the extrapolation of data from one site or year to the population level, and hence for their management and conservation.     

Small‐angle scattering for structural biology—Expanding the frontier while avoiding the pitfalls

The last decade has seen a dramatic increase in the use of small‐angle scattering for the study of biological macromolecules in solution. The drive for more complete structural characterization of proteins and their interactions, coupled with the increasing availability of instrumentation and easy‐to‐use software for data analysis and interpretation, is expanding the utility of the technique beyond the domain of the biophysicist and into the realm of the protein scientist. However, the absence of publication standards and the ease with which 3D models can be calculated against the inherently 1D scattering data means that an understanding of sample quality, data quality, and modeling assumptions is essential to have confidence in the results. This review is intended to provide a road map through the small‐angle scattering experiment, while also providing a set of guidelines for the critical evaluation of scattering data. Examples of current best practice are given that also demonstrate the power of the technique to advance our understanding of protein structure and function.     

Functional hot spots in human ATP-binding cassette transporter nucleotide binding domains

The human ATP‐binding cassette (ABC) transporter superfamily consists of 48 integral membrane proteins that couple the action of ATP binding and hydrolysis to the transport of diverse substrates across cellular membranes. Defects in 18 transporters have been implicated in human disease. In hundreds of cases, disease phenotypes and defects in function can be traced to nonsynonymous single nucleotide polymorphisms (nsSNPs). The functional impact of the majority of ABC transporter nsSNPs has yet to be experimentally characterized. Here, we combine experimental mutational studies with sequence and structural analysis to describe the impact of nsSNPs in human ABC transporters. First, the disease associations of 39 nsSNPs in 10 transporters were rationalized by identifying two conserved loops and a small α‐helical region that may be involved in interdomain communication necessary for transport of substrates. Second, an approach to discriminate between disease‐associated and neutral nsSNPs was developed and tailored to this superfamily. Finally, the functional impact of 40 unannotated nsSNPs in seven ABC transporters identified in 247 ethnically diverse individuals studied by the Pharmacogenetics of Membrane Transporters consortium was predicted. Three predictions were experimentally tested using human embryonic kidney epithelial (HEK) 293 cells stably transfected with the reference multidrug resistance transporter 4 and its variants to examine functional differences in transport of the antiviral drug, tenofovir. The experimental results confirmed two predictions. Our analysis provides a structural and evolutionary framework for rationalizing and predicting the functional effects of nsSNPs in this clinically important membrane transporter superfamily.     

太湖粳稻同名地方品种的遗传差异

选用45个SSR标记分析太湖流域荔枝红、老来青、太湖青和老虎稻共4组粳稻同名地方品种的遗传差异。结果表明:同名地方品种平均Nei遗传距离为0.120~0.171,遗传同一性程度较高,其中有8对同名品种难以区别,但多数品种仍然存在一定的遗传变异,且个别品种差异较大;同名品种遗传差异与种质来源、品种名称的近似程度没有关系。     

Dental and phylogeographic patterns of variation in gorillas

Gorilla patterns of variation have great relevance for studies of human evolution. In this study, molar morphometrics were used to evaluate patterns of geographic variation in gorillas. Dental specimens of 323 adult individuals, drawn from the current distribution of gorillas in equatorial Africa were divided into 14 populations. Discriminant analyses and Mahalanobis distances were used to study population structure.Results reveal that: 1) the West and East African gorillas form distinct clusters, 2) the Cross River gorillas are well separated from the rest of the western populations, 3) gorillas from the Virunga mountains and the Bwindi Forest can be differentiated from the lowland gorillas of Utu and Mwenga-Fizi, 4) the Tshiaberimu gorillas are distinct from other eastern gorillas, and the Kahuzi-Biega gorillas are affiliated with them. These findings provide support for a species distinction between Gorilla gorilla and Gorilla beringei, with subspecies G. g. diehli, G. g. gorilla, G. b. graueri, G. b. beringei, and possibly, G. b. rex-pygmaeorum. Clear correspondence between dental and other patterns of taxonomic diversity demonstrates that dental data reveal underlying genetic patterns of differentiation.Dental distances increased predictably with altitude but not with geographic distances, indicating that altitudinal segregation explains gorilla patterns of population divergence better than isolation-by-distance. The phylogeographic pattern of gorilla dental metric variation supports the idea that Plio-Pleistocene climatic fluctuations and local mountain building activity in Africa affected gorilla phylogeography. I propose that West Africa comprised the historic center of gorilla distribution and experienced drift-gene flow equilibrium, whereas Nigeria and East Africa were at the periphery, where climatic instability and altitudinal variation promoted drift and genetic differentiation. This understanding of gorilla population structure has implications for gorilla conservation, and for understanding the distribution of sympatric chimpanzees and Plio-Pleistocene hominins.     

Relationship of cranial robusticity to cranial form,geography and climate in Homo sapiens

Variation in cranial robusticity among modern human populations is widely acknowledged but not well‐understood. While the use of “robust” cranial traits in hominin systematics and phylogeny suggests that these characters are strongly heritable, this hypothesis has not been tested. Alternatively, cranial robusticity may be a response to differences in diet/mastication or it may be an adaptation to cold, harsh environments. This study quantifies the distribution of cranial robusticity in 14 geographically widespread human populations, and correlates this variation with climatic variables, neutral genetic distances, cranial size, and cranial shape. With the exception of the occipital torus region, all traits were positively correlated with each other, suggesting that they should not be treated as individual characters. While males are more robust than females within each of the populations, among the independent variables (cranial shape, size, climate, and neutral genetic distances), only shape is significantly correlated with inter‐population differences in robusticity. Two‐block partial least‐squares analysis was used to explore the relationship between cranial shape (captured by three‐dimensional landmark data) and robusticity across individuals. Weak support was found for the hypothesis that robusticity was related to mastication as the shape associated with greater robusticity was similar to that described for groups that ate harder‐to‐process diets. Specifically, crania with more prognathic faces, expanded glabellar and occipital regions, and (slightly) longer skulls were more robust than those with rounder vaults and more orthognathic faces. However, groups with more mechanically demanding diets (hunter‐gatherers) were not always more robust than groups practicing some form of agriculture. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.