Landscape genetic structure of <Emphasis Type="Italic">Olea europaea</Emphasis> subsp. <Emphasis Type="Italic">cuspidata</Emphasis> in Ethiopian highland forest fragments

Understanding patterns of genetic diversity at the landscape scale will enhance conservation and management of natural populations. Here we analyzed the genetic diversity, population connectivity, and spatial genetic structure among subpopulations and age groups of Olea europaea subsp. cuspidata, a cornerstone species of the Afromontane highlands. The study was conducted at the landscape level within a radius of approximately 4 km, as well as on a fine scale (intensive study plot) of less than 300 m radius. In total 542 samples from four natural subpopulations in northwestern Ethiopia were analyzed using ten nuclear microsatellite markers. Inbreeding was higher in smaller populations. No genetic difference was detected among cohorts of different tree sizes in the intensive studied plot. Average population differentiation was low but significant (F _ST ?=?0.016). Landscape genetic analysis inferred two groups: the most distant subpopulation WE located less than 4 kms from the other three subpopulations formed a separate group. Sixty-four percent of the total migrants were shared among the three latter subpopulations, which are spatially clustered. Immigrants were non-randomly distributed inside of the intensive study plot. Significant spatial genetic structure (SGS) was found both at the landscape scale and in the intensive study plot, and adults showed stronger SGS than young trees. An indirect estimate of 220 m as mean gene dispersal distance was obtained. We conclude that even under fragmentation migration is not disrupted in wild olive trees and that large protected populations at church forests are very important to conserve genetic resources. However, the higher level of inbreeding and evidence for population bottlenecks in the small populations, as well as the persisting heavy pressure on most remaining populations, warrants quick action to maintain genetic diversity of wild olive in the Ethiopian highlands.     

Movements and source–sink dynamics of a Masai giraffe metapopulation

Spatial variation in habitat quality and anthropogenic factors, as well as social structure, can lead to spatially structured populations of animals. Demographic approaches can be used to improve our understanding of the dynamics of spatially structured populations and help identify subpopulations critical for the long-term persistence of regional metapopulations. We provide a regional metapopulation analysis to inform conservation management for Masai giraffes (Giraffa camelopardalis tippelskirchi) in five subpopulations defined by land management designations. We used data from an individual-based mark–recapture study to estimate subpopulation sizes, subpopulation growth rates, and movement probabilities among subpopulations. We assessed the source–sink structure of the study population by calculating source–sink statistics, and we created a female-based matrix metapopulation model composed of all subpopulations to examine how variation in demographic components of survival, reproduction, and movement affected metapopulation growth rate. Movement data indicated no subpopulation was completely isolated, but movement probabilities varied among subpopulations. Source–sink statistics and net flow of individuals indicated three subpopulations were sources, while two subpopulations were sinks. We found areas with higher wildlife protection efforts and fewer anthropogenic impacts were sources, and less-protected areas were identified as sinks. Our results highlight the importance of identifying source–sink dynamics among subpopulations for effective conservation planning and emphasize how protected areas can play an important role in sustaining metapopulations.     

Identification of various testicular cell populations in pubertal and adult cockerels

Precise identification of the male germinal stem cell population is important for their practical use in programs dedicated to the integration of exogenous genetic material in testicular tissues. In the present study, our aim was to identify germinal cell populations in the testes of pubertal and adult cockerels based on the detection of the nuclear DNA content by fluorescence-activated cell sorting (FACS) and on the expression of the Dazl and Stra8 genes in single-cell suspensions of testicular tissues. Cells with a tetraploid DNA content (4c) represent a small and equal fraction of the total germinal cell population in both pubertal and adult males. In contrast, the diploid (2c) and haploid (c) subpopulations differ significantly between ages as a consequence of different degrees of sexual maturation. A specific subpopulation of testicular cells, the side-scatter subpopulation of cells, or side population (SP), was identified at the junction between the haploid and diploid cell populations. The percentage of this cell subpopulation differs significantly in pubertal and adult cockerels, accounting for 4.1% and 1.3% of the total cell population, respectively. These four testicular cell populations were also tested for the expression of Dazl and Stra8 genes known to be expressed in premeiotic cells including stem spermatogonia. Both genes were expressed in SP, whereas the expression of either Dazl or Stra8 genes was detected only in the 4c and in the 2c testicular cell subpopulations, respectively. The correlation between the cell ploidy and Dazl/Stra8 expression was the same at both male ages. We conclude that SP cells might represent a subpopulation of germinal cells enriched in stem spermatogonia, which can be of great importance for transgenesis in chicken.     

Costs and benefits of group living with disease: a case study of pneumonia in bighorn lambs (Ovis canadensis)

Group living facilitates pathogen transmission among social hosts, yet temporally stable host social organizations can actually limit transmission of some pathogens. When there are few between-subpopulation contacts for the duration of a disease event, transmission becomes localized to subpopulations. The number of per capita infectious contacts approaches the subpopulation size as pathogen infectiousness increases. Here, we illustrate that this is the case during epidemics of highly infectious pneumonia in bighorn lambs (Ovis canadensis). We classified individually marked bighorn ewes into disjoint seasonal subpopulations, and decomposed the variance in lamb survival to weaning into components associated with individual ewes, subpopulations, populations and years. During epidemics, lamb survival varied substantially more between ewe-subpopulations than across populations or years, suggesting localized pathogen transmission. This pattern of lamb survival was not observed during years when disease was absent. Additionally, group sizes in ewe-subpopulations were independent of population size, but the number of ewe-subpopulations increased with population size. Consequently, although one might reasonably assume that force of infection for this highly communicable disease scales with population size, in fact, host social behaviour modulates transmission such that disease is frequency-dependent within populations, and some groups remain protected during epidemic events.     

Integration of genetic and demographic data to assess population risk in a continuously distributed species

The identification and demographic assessment of biologically meaningful populations is fundamental to species’ ecology and management. Although genetic tools are used frequently to identify populations, studies often do not incorporate demographic data to understand their respective population trends. We used genetic data to define subpopulations in a continuously distributed species. We assessed demographic independence and variation in population trends across the distribution. Additionally, we identified potential barriers to gene flow among subpopulations. We sampled greater sage-grouse (Centrocercus urophasianus) leks from across their range (≈175,000 Km²) in Wyoming and amplified DNA at 14 microsatellite loci for 1761 samples. Subsequently, we assessed population structure in unrelated individuals (n = 872) by integrating results from multiple Bayesian clustering approaches and used the boundaries to inform our assessment of long-term population trends and lek activity over the period of 1995–2013. We identified four genetic clusters of which two northern ones showed demographic independence from the others. Trends in population size for the northwest subpopulation were statistically different from the other three genetic clusters and the northeast and southwest subpopulations demonstrated a general trend of increasing proportion of inactive leks over time. Population change from 1996 to 2012 suggested population growth in the southern subpopulations and decline, or neutral, change in the northern subpopulations. We suggest that sage-grouse subpopulations in northern Wyoming are at greater risk of extirpation than the southern subpopulations due to smaller census and effective population sizes and higher variability within subpopulations. Our research is an example of incorporating genetic and demographic data and provides guidance on the identification of subpopulations of conservation concern.     

Evaluating sample allocation and effort in detecting population differentiation for discrete and continuously distributed individuals

One of the most pressing issues in spatial genetics concerns sampling. Traditionally, substructure and gene flow are estimated for individuals sampled within discrete populations. Because many species may be continuously distributed across a landscape without discrete boundaries, understanding sampling issues becomes paramount. Given large-scale, geographically broad conservation efforts, researchers are looking for guidance as to the trade-offs between sampling more individuals within a population versus few individuals scattered across more populations. Here, we conducted simulations that address these issues. We first established two archetypical patterns of dispersion: (1) individuals within discrete populations, and (2) continuously distributed individuals with limited dispersal. We used genotypes generated from a spatially-explicit, individual-based program and simulated genetic structure in individuals from nine different population sizes across a landscape that either had barriers to movement (defining discrete populations) or isolation-by-distance patterns (defining continuously distributed individuals). Then, given each pattern of dispersion, we allocated samples across four different sampling strategies for each of the nine population sizes in various configurations for sampling more individuals within a population versus fewer individuals scattered across more populations. We assessed the population genetic substructure with both the population-based metric, F _ST, and an individual-based metric, D _PS regardless of the true pattern of dispersion to allow us to better understand the effect of incorrectly matching the metric and the distribution (e.g., F _ST with continuously distributed individuals, and vice versa). We show that sampling many subpopulations (or sampling areas), thus sampling fewer individuals per subpopulation, overestimates measures of population subdivision with the population-based metric for both patterns of dispersion. In contrast, using the individual-based metric gives the opposite results: sampling too few subpopulations, and many individuals per subpopulation, produces an underestimate of the strength of isolation-by-distance. By comparing all results, we were able to suggest a strong predictive model of a chosen genetic structure metric for elucidating the sampling design trade-offs given each pattern of dispersion and configuration on the landscape.     

Population size estimation in a two-list surveillance system with a discrete covariate

Summary .   Capture–recapture methods are widely adopted to estimate sizes of populations of public health interest using information from surveillance systems. For a two-list surveillance system with a discrete covariate, a population is divided into several subpopulations. A unified framework is proposed in which the logits of presence probabilities are decomposed into case effects and list effects. The estimators for the whole population and subpopulation sizes, their adjusted versions, and asymptotic standard errors admit closed-form expressions. Asymptotic and bootstrap individual and simultaneous confidence intervals are easily constructed. Conditional likelihood ratio tests are used to select one from three possible models. Real examples are investigated.     

Mating pattern and pollen dispersal in the wild olive tree (<Emphasis Type="Italic">Olea europaea</Emphasis> subsp. <Emphasis Type="Italic">cuspidata</Emphasis>)

In this study, the mating system, contemporary pollen flow, and landscape pollen connectivity of the wild olive tree (Olea europaea subsp. cuspidata) were analyzed in a fragmented landscape of less than 4-km diameter located in north-western Ethiopia. Four remnant populations of different sizes were investigated. Eight highly polymorphic microsatellite markers were used to genotype 534 adults and 704 embryos. We used contrasting sampling schemes and different methodological approaches to analyze the pollen flow. We observed a lower rate of inbreeding and correlated mating in the fragmented vs. the non-fragmented subpopulation. Using parentage analysis, we detected a bidirectional pollen movement across subpopulations. Pollen flow was found to be directed towards small subpopulations based on parentage and anisotropic analysis. Pollen immigration amounted to more than 50%. Although most pollination occurred within a distance of less than 200 m, longer distance pollen movements of more than 3 km were also detected. Pollen dispersal in the large and dense subpopulation was reduced, and a smaller number of effective pollen sources were detected compared to a smaller fragmented subpopulation. We obtained consistent estimates for the number of effective pollen donors (approximately 6 per mother tree) using three different methods. The average pollen dispersal distance at the landscape level amounted to 276 m while at the local level, 174 m was estimated. Bigger trees were better pollen contributors than smaller trees. We showed here for the first time that pollen dispersal in wild olive follows a leptokurtic distribution.     

Population viability analysis of Saxifraga cotyledon,a perennial plant with semelparous rosettes

The aim with this study was to analyse the population dynamics ofSaxifraga cotyledon, a rare, long lived herb, withsemelparous rosettes. In Sweden, S. cotyledon grows infragmented habitats at high altitude and is classified as vulnerable accordingto the IUCN system. From a five year demographical study we estimatedpopulationgrowth rates and extinction risks for one small and one large subpopulation. Inthe small subpopulation deterministic matrix simulations showed largevariation,with two transitions projecting negative and two projecting positive populationgrowth. The large subpopulation also showed large variation, but all yearlytransitions projected positive population growth. In both subpopulationssurvival and growth contributed more than twice as much to population growthrates than did sexual reproduction, vegetative reproduction and the seed bankall taken together. In stochastic simulations the maximum likelihood growthestimator waslarger than 1 for both subpopulations. None of the two subpopulations sufferfrom high extinction rates and although the effect of demographic stochasticityincrease extinction risk in small populations it is enough with 70 individualsfor a viable population of S. cotyledon. Hence, for thestudied population of S. cotyledon, rareness per se is nota good indicator of vulnerability.     

Phosphatidylserine exposure by Toxoplasma gondii is fundamental to balance the immune response granting survival of the parasite and of the host

Phosphatidylserine (PS) exposure on the cell surface indicates apoptosis, but has also been related to evasion mechanisms of parasites, a concept known as apoptotic mimicry. Toxoplasma gondii mimics apoptotic cells by exposing PS, inducing secretion of TGF-beta1 by infected activated macrophages leading to degradation of inducible nitric oxide (NO) synthase, NO production inhibition and consequently persisting in these cells. Here PS⁺ and PS⁻ subpopulation of tachyzoites were separated and the entrance mechanism, growth and NO inhibition in murine macrophages, and mice survival and pathology were analyzed. Infection index in resident macrophages was similar for both PS subpopulations but lower when compared to the total T. gondii population. Growth in resident macrophages was higher for the total T. gondii population, intermediate for the PS⁺ and lower for the PS⁻ subpopulation. Production of NO by activated macrophages was inhibited after infection with the PS⁺ subpopulation and the total populations of tachyzoites. However, the PS⁻ subpopulation was not able to inhibit NO production. PS⁺ subpopulation invaded macrophages by active penetration as indicated by tight-fitting vacuoles, but the PS⁻ subpopulation entered macrophages by phagocytosis as suggested by loose-fitting vacuoles containing these tachyzoites. The entrance mechanism of both subpopulations was confirmed in a non-professional phagocytic cell line where only the PS⁺ tachyzoites were found inside these cells in tight-fitting vacuoles. Both subpopulations of T. gondii killed mice faster than the total population. Clear signs of inflammation and no tachyzoites were seen in the peritoneal cavity of mice infected with the PS⁻ subpopulation. Moreover, mice infected with the PS⁺ subpopulation had no sign of inflammation and the parasite burden was intense. These results show that PS⁺ and PS⁻ subpopulations of T. gondii are necessary for a successful toxoplasma infection indicating that both subpopulations are required to maintain the balance between inflammation and parasite growth.     

Demographic history of a common pioneer tree,Zanthoxylum ailanthoides,reconstructed using isolation-with-migration model

The Japanese prickly ash, Zanthoxylum ailanthoides Siebold & Zucc. (Rutaceae), is one of the most common pioneer tree species that grow in disturbed areas, such as canopy gaps, in Japanese warm-temperate evergreen oak forests. The strong genetic structure of its current population might suggest long-term isolation of subpopulations by demographic events, in addition to ecological features of this species. Analyses of genome-wide nucleotide variation using model-based approaches are necessary to achieve a good understanding of the demographic history of a species. In this study, we analyzed the nucleotide variation in natural populations of Z. ailanthoides using a computer program that applied the isolation-with-migration model to quantitatively infer the demographic history. Nucleotide variations at 10 or 26 nuclear loci in six populations from a wide range of the species distribution were analyzed. The maximum likelihood estimate of the divergence time between the current populations in the two hypothetical refugia of Z. ailanthoides was approximately 24,000 years. Unexpectedly, the estimated size of the ancestral population was larger than the sizes of the two current populations. The results suggested a relatively recent divergence of these two populations and rapid formation of strong genetic structure among subpopulations. The large ancestral population may indicate a more complex demographic history during or after the last glacial period than the simple isolation-with-migration model implies.     

Comparison of VNTR allele frequencies and inclusion probabilities over six populations

There is considerable debate about the methodologies used to estimate VNTR (Variable Number of Tandem Repeats) multi-locus genotype frequencies or odds of inclusion in forensic cases. To compare two of the methods in use, allele frequency distributions among six populations were compared and the effect of population heterogeneity on VNTR multi-locus genotype frequency estimation was examined. Genotype frequencies estimated from single population data were one or two orders of magnitude smaller than those estimated by picking the highest allele frequency in a group of subpopulations to estimate genotype frequencies using a ceiling principle. The average change does not appear to be very sensitive to the set of subpopulations used; four locus frequencies still give inclusion odds of one in a million or less. We think that use of the ceiling principle solves both the statistical problem engendered by subpopulation heterogeneity and the legal problem of assuming that the prepetrator and suspect belong to the same subpopulation. The counterintuitive fact of human genetic polymorphism is that it is easier to identify an individual than it is to identify the subpopulation, ethnic group or race to which that individual belongs.     

An experimental evaluation with Drosophila melanogaster of a novel dynamic system for the management of subdivided populations in conservation programs

A dynamic method (DM) recently proposed for the management of captive subdivided populations was evaluated using the pilot species Drosophila melanogaster. By accounting for the particular genetic population structure, the DM determines the optimal mating pairs, their contributions to progeny and the migration pattern that minimize the overall coancestry in the population with a control of inbreeding levels. After a pre-management period such that one of the four subpopulations had higher inbreeding and differentiation than the others, three management methods were compared for 10 generations over three replicates: (1) isolated subpopulations (IS), (2) one-migrant-per-generation rule (OMPG), (3) DM aimed to produce the same or lower inbreeding coefficient than OMPG. The DM produced the lowest coancestry and equal or lower inbreeding than the OMPG method throughout the experiment. The initially lower fitness and lower variation for nine microsatellite loci of the highly inbred subpopulation were restored more quickly with the DM than with the OMPG method. We provide, therefore, an empirical illustration of the usefulness of the DM as a conservation protocol for captive subdivided populations when pedigree information is available (or can be deduced) and manipulation of breeding pairs is possible.     

Evaluation of the geographical pattern of genetic diversity of Glycine soja and Glycine max based on four single copy nuclear gene loci: For conservation of soybean germplasm

Genetic diversity and its geographical patterns play a very important role in species conservation and exploitation. Here, nucleotide polymorphism patterns of four single copy nuclear gene loci in wild (Glycine soja) and cultivated soybean (Glycine max) populations from different geographical regions as well as their demographic history were analyzed. The results showed that: (1) Southern subpopulation has the highest, while central subpopulation revealed the lowest genetic diversity among three Chinese G. soja subpopulations. (2) Northern Chinese G. max subpopulation depicted higher genetic diversity than other two Chinese, Korean, Japanese and American G. max subpopulations. (3) Significant genetic differentiation (P < 0.001) was observed among Chinese G. soja subpopulations from three ecological zones. There was also a significant genetic differentiation（P < 0.01）between three Chinese and Japanese subpopulations of G. max. (4) The demographic dynamics revealed that effective population size of G. soja is expanding, while it was constant in G. max. G. soja is a useful germplasm resource to widen the genetic diversity of G. max. This study suggests that native populations of G. soja from different geo-ecological regions should be protected to conserve the genetic diversity.     

Directional gene flow patterns in disjunct populations of the black ratsnake (Pantheropis obsoletus) and the Blanding’s turtle (Emydoidea blandingii)

The estimation and maintenance of connectivity among local populations is an important conservation goal for many species at risk. We used Bayesian statistics and coalescent theory to estimate short- and long-term directional gene flow among subpopulations for two reptiles that occur in Canada as peripheral populations that are geographically disjunct from the core of their respective species’ ranges: the black ratsnake and the Blanding’s turtle. Estimates of directional gene flow were used to examine population connectivity and potential genetic source-sink dynamics. For both species, our estimates of directional short- and long-term gene flow were consistently lower than estimates inferred previously from F _ST measures. Short- and long-term gene flow estimates were discordant in both species, suggesting that population dynamics have varied temporally in both species. These estimates of directional gene flow were used to identify specific subpopulations in both species that may be of high conservation value because they are net exporters of individuals to other subpopulations. Overall, our results show that the use of more sophisticated methods to evaluate population genetic data can provide valuable information for the conservation of species at risk, including bidirectional estimates of subpopulation connectivity that rely on fewer assumptions than more traditional analyses. Such information can be used by conservation practitioners to better understand the geographic scope required to maintain a functional metapopulation, determine which habitat corridors within a working landscape may be most important to maintain connectivity among subpopulations, and to prioritize subpopulations with respect to their potential to act as genetic sources within the metapopulation.     

Estimation of migration rates from marker‐based parentage analysis

Coupled with rapid developments of efficient genetic markers, powerful population genetic methods were proposed to estimate migration rates (m) in natural populations in much broader spatial and temporal scales than the traditional mark‐release‐recapture (MRR) methods. Highly polymorphic (e.g. microsatellites) and genomic‐wide (e.g. SNPs) markers provide sufficient information to assign individuals to their populations or parents of origin and thereby to estimate directly m in a way similar to MRR. Such direct estimates of current migration rates are particularly useful in understanding the ecology and microevolution of wild populations and in managing the populations in the future. In this study, I proposed and implemented, in the software MigEst, a likelihood method to use marker‐based parentage assignments in jointly estimating m and candidate parent sampling proportions (x) in a subset of populations, investigated its power and accuracy using data simulated in various scenarios of population properties (e.g. the actual m, number, size and differentiation of populations) and sampling properties (e.g. the numbers of sampled parent candidates, offspring and markers), compared it with the population assignment approach implemented in the software BayesAss and demonstrated its usefulness by analysing a microsatellite data set from three natural populations of Brazilian bats. Simulations showed that MigEst provides unbiased and accurate estimates of m and performs better than BayesAss except when populations are highly differentiated with very small and ecologically insignificant migration rates. A valuable property of MigEst is that in the presence of unsampled populations, it gives good estimates of the rate of migration among sampled populations as well as of the rate of migration into each sampled population from the pooled unsampled populations.     

Isolated in an ocean of grass: low levels of gene flow between termite subpopulations

Habitat fragmentation is one of the most important causes of biodiversity loss, but many species are distributed in naturally patchy habitats. Such species are often organized in highly dynamic metapopulations or in patchy populations with high gene flow between subpopulations. Yet, there are also species that exist in stable patchy habitats with small subpopulations and presumably low dispersal rates. Here, we present population genetic data for the ‘magnetic’ termite Amitermes meridionalis, which show that short distances between subpopulations do not hinder exceptionally strong genetic differentiation (F_ST: 0.339; R_ST: 0.636). Despite the strong genetic differentiation between subpopulations, we did not find evidence for genetic impoverishment. We propose that loss of genetic diversity might be counteracted by a long colony life with low colony turnover. Indeed, we found evidence for the inheritance of colonies by so‐called ‘replacement reproductives’. Inhabiting a mound for several generations might result in loss of gene diversity within a colony but maintenance of gene diversity at the subpopulation level.     

Stabilizing Spatially-Structured Populations through Adaptive Limiter Control

Stabilizing the dynamics of complex, non-linear systems is a major concern across several scientific disciplines including ecology and conservation biology. Unfortunately, most methods proposed to reduce the fluctuations in chaotic systems are not applicable to real, biological populations. This is because such methods typically require detailed knowledge of system specific parameters and the ability to manipulate them in real time; conditions often not met by most real populations. Moreover, real populations are often noisy and extinction-prone, which can sometimes render such methods ineffective. Here, we investigate a control strategy, which works by perturbing the population size, and is robust to reasonable amounts of noise and extinction probability. This strategy, called the Adaptive Limiter Control (ALC), has been previously shown to increase constancy and persistence of laboratory populations and metapopulations of Drosophila melanogaster. Here, we present a detailed numerical investigation of the effects of ALC on the fluctuations and persistence of metapopulations. We show that at high migration rates, application of ALC does not require a priori information about the population growth rates. We also show that ALC can stabilize metapopulations even when applied to as low as one-tenth of the total number of subpopulations. Moreover, ALC is effective even when the subpopulations have high extinction rates: conditions under which another control algorithm had previously failed to attain stability. Importantly, ALC not only reduces the fluctuation in metapopulation sizes, but also the global extinction probability. Finally, the method is robust to moderate levels of noise in the dynamics and the carrying capacity of the environment. These results, coupled with our earlier empirical findings, establish ALC to be a strong candidate for stabilizing real biological metapopulations.     

EVIDENCE OF PARTIAL APOMIXIS IN ANTENNARIA MEDIA (ASTERACEAE: INULEAE) DETECTED BY THE SEGREGATION OF GENETIC MARKERS

The interplant variation in sexual and asexual reproduction in an Oregon population of the alpine perennial Antennaria media was investigated. Four polymorphic loci were assayed by enzyme electrophoresis of the progeny of 72 families from two subpopulations of A. media. The population was divided into two spatially distinct subpopulations. A multilocus model, incorporating a mixture of apomixis and random outcrossing, was used to estimate the mating system of pistillate plants both on the population and individual levels with statistical significance of the estimates based on bootstrap methods. The population contained a mixture of sexual individuals, partial apomicts, and obligate apomicts. The first subpopulation contained individuals that were partially apomictic and presumably produced both reduced and unreduced embryo sacs. There was a conspicuous difference in the breeding system composition between the two subpopulations. The first subpopulation had a “female” biased gender ratio and contained mostly obligate apomicts, some partial apomicts, and some outcrossing amphimicts. The second subpopulation, which had a nearly balanced gender ratio, contained mostly amphimicts, some obligate apomicts, but no facultative apomicts. This is the first study to document partial apomixis in individual plants by the use of genetic markers.     

Identification of subpopulations of North American elk (Cervus elaphus L.) using multiple lines of evidence: habitat use, dietary choice, and fecal stable isotopes

We used multiple lines of evidence to assess habitat selection, dietary choice, and nutritional outcomes for a population of North American elk (Cervus elaphus), confined to a relatively small and isolated landscape of public and private land in south-central Great Plains, USA. The area of suitable elk habitat was a topographically diverse matrix of mature oak savannah, C₄-dominated grasslands, and C₃-dominated agricultural fields surrounded by unsuitable lowlands fragmented by anthropogenic activities. We hypothesized that such disparity in habitat availability and quality resulted in subpopulation differences in the overall elk population. We used 3 methods to evaluate this premise: radiotelemetry to determine home range and habitat use, microhistology of plant fragments in feces to determine dietary selection, and fecal nitrogen (N) and stable isotope ratios of nitrogen (δ¹⁵N) and carbon (δ¹³C) to assess nutritional outcomes of habitat use and dietary choice. By comparing these 3 approaches, we wanted to determine if fecal indices alone could efficiently and accurately identify subpopulation structuring. Compositional analyses from radiotelemetry observations of 21 female elk identified 2 subpopulations that occupied relatively disjunct areas and showed differential preferences for forested and cultivated fields in summer but comparable preferences for cultivated fields in winter. A third unmarked subpopulation of elk was known to be largely confined to an adjacent wildlife refuge. Microhistological analyses of feces collected in all 3 areas highlighted distinct diets, outcomes of habitat occupation by the 3 subpopulations. Increased use of cultivated forages in winter was evident for 2 of the subpopulations, but the extent of use by elk was dependent on availability of cultivated forages in areas they occupied. The refuge subpopulation had no access to cultivated forage. Fecal N, fecal δ¹³C, and fecal δ¹⁵N supported the premise that the subpopulation with the greatest access to cultivated forages was on a higher nutritional plane than the other 2 subpopulations. Changes in fecal N, fecal δ¹³C, and fecal δ¹⁵N paralleled percentages of cultivated forages in the diets highlighting the utility of such fecal indices as supplemental to or surrogates for traditional methods of habitat use and dietary selection in free-ranging ungulates.