Population ecology

Eradication programs for invasive species
can benefit from tools that delineate infestations and
identify patterns of spread to guide eradication priorities
and activities. However, identifying these patterns
in cryptic organisms such the Asian longhorned
beetle can be complicated by the sometimes conflicting
needs of rapid eradication and research. Here, we
describe the use of a simple approach based on tools
and concepts used in graph theory to infer beetle
movement, using infested tree records collected by the
Asian Longhorned Beetle Eradication Program in
Worcester, MA, the largest infestation yet found in the
U.S. Analyses included two sets of assumptions about
beetle dispersal (representing a gap in knowledge of
beetle biology), and two data sets of varying completeness,
which were combined to develop and
compare four scenarios of beetle dispersal in
Worcester, MA. Together, these four scenarios suggest
that the shape of the beetle dispersal-distance
probability curve or dispersal kernel is more sensitive
to assumptions about the predilection of beetles to
disperse than to the size and completeness of the
infested tree database, though both impacted inferred
patterns of dispersal. The four scenarios are used to
produce empirical estimates of dispersal risk around
the current infestation, which can inform eradication
efforts while recognizing the limits of data availability
in a rapidly evolving eradication program. These
estimates of dispersal also highlight the importance of
continuing to integrate data collection into eradication
programs, and the need to expand our understanding of
beetle behavior and biology, as the data shown suggest
that differences in dispersal behavior could dictate
different eradication strategies.

Adaptation assessment cenopopulation Aegilops ovata
L. in recreation.
The effect of trampling on morphometric parameters сenopopulatiоn one-year grass
Aegilops ovata L. on the southern coast of Crimea is examined and their adaptive possibilities
are determined. The results of the statistical analysis of quantitative and qualitative parameters
cenopopulation Aegilops are produced. Conducted vitality analysis showed that
cenopopulation A. ovata in recreational pressure is prosperous. Established reactivity cenopopulation
Aegilops ovata L. the impact of trampling characterized by a significant reduction
in the scale of individuals and vegetative organs and stable values of the investigated
parameters of the generative organs. The environmental conditions of growth for A. ovata
are optimal, and trampling did not cause significant damage to plants.
Keywords: cenopopulation, recreation, indicator, morphometric features, Aegilops
ovata, ecological features, vitality spectrum.

Andean Condors (Vultur gryphus) are a Near Threatened species that was formerly distributed along the entire length of the Andes from western Venezuela to Tierra del Fuego. Populations have been severely reduced north of Peru, but several thousand Andean Condors still exist in the southern portion of their range in Argentina and Chile. Little is known, however, about the size of the Andean Condor population in the central part of their range in Peru and Bolivia. From June to September 2012, we used feeding stations to attract Andean
Condors and estimate the size and structure of the population in the eastern Andes of central and southern Bolivia.
We estimated a minimum population of 253 condors, an adult male-to-female ratio of 1:0.6, an immature maleto-female
ratio of 1:0.9, and an adult-to-immature ratio of 1:1.1. At our five survey areas, estimated abundance ranged from 15 to 100 condors per area. Males outnumbered females in three areas and the opposite was true in two areas. Our estimated adult-to-immature ratio, overall and in each area, suggests that the populations could be reproducing at a high rate. As previously observed in other Andean Condor populations, skewed sex ratios could be associated with differences between sexes and age classes in habitat selection. Although our results suggest
that Bolivian populations of Andean Condors are still reasonably large, population monitoring is urgently needed,
including use of feeding stations throughout the entire Bolivian range of the species and intensive searches for roosting and nesting sites.

How can this paper better elucidate conditions currently being faced and projected to exist in the twenty-first century? In the last hundred years human population has increased 400%. In 1927 there were approximately 2.5 billion people; currently there are 7.3 billion and it is projected that by 2025 there will likely be 8 billion.  This is not promising.

Phylogeographical studies using DNA markers offer great insight to species genetic patterns and help to appreciate how the environment can influence structure. Macrobrachium australiense, a freshwater prawn species of eastern Australia, was the subject of a population genetics investigation to determine if hypothesised genetic structure is a result of the stream hierarchy model (SHM) for catchments in western Queensland and south east Queensland. The cytochrome oxidase I (COI) gene (mtDNA) was selected as a surrogate for estimating genetic structure by haplotype and molecular diversity indices, mismatch analysis, pairwise FST and AMOVA. Analyses found considerable population divergence overall (FST = 0.8613). Subpopulations were isolated by distance in the western Queensland catchments. Alternatively, south east Queensland subcatchments were found to be genetically similar and panmictic.

Tourism development is one of the main contemporary drivers of habitat loss and fragmentation
within the Caribbean Islands biodiversity hotspot. In Saint Lucia, construction of a hotel and golf
course within coastal dry forest is directly threatening the largest known subpopulation of the
Endangered White-breasted Thrasher Ramphocinclus brachyurus. Understanding how the species is
responding to ongoing landscape change and identifying priority sites for conservation are imperative
for planning its long-term conservation. In this study, a four year White-breasted Thrasher monitoring
dataset (2006–2009) and landscape-scale environmental variables were used to: a) identify,
characterise and map spatio-temporal patterns of White-breasted Thrasher encounter rate (an abundance
proxy) within and outside the tourist development site; b) determine landscape-scale environmental
variables that influence such patterns, and c) produce an island-wide predictive map of
potentially suitable habitat. Observed patterns in encounter rates within and outside the development
site were consistent with thrashers being displaced from cleared areas of forest and crowding into
intact forest patches to the north and west of the golf course. A year after the period of the most
extensive habitat clearance, White-breasted Thrasher numbers declined markedly leading to a 55%
reduction in encounter rate within the development site over the four years of the study. The habitat
suitability model predicted that a range of sites outside of the known geographic range of the thrasher
are potentially suitable, some of which merit further surveys for potentially undetected populations.
Given these findings, it is vital that patches of suitable dry forest adjacent to the tourist development
are protected and contiguous natural habitat inside the tourist development is preserved.

The focus on either isolation or connectivity in discussions of the social relations of prehistoric islanders has been polarizing. This paper advances the debate beyond this dichotomy by proposing a general and cross-cultural model of adaptive behavioral responses to stochastically-forced demographic fragility. It is shown that smaller populations – more likely earlier in the settlement histories of islands – are more exposed to localized extinction via stochastic processes. To alleviate this greater degree of exposure, maintaining social links which allow for genetic flow between otherwise isolated populations should increase overall fitness. Conversely, as discrete populations expand, the imperative for access to a widely distributed metapopulation, and hence the need to maintain these links, should decrease. This is illustrated via simple network analysis. Potential venues for testing this general model are outlined; wider implications for the archaeology of colonization, and for spatial modeling of social interaction, are briefly discussed

Estimates of annual survival rates of birds are valuable in a wide range of studies of population ecology and conservation.  These include modelling studies to assess the impacts of climatic change and anthropogenic mortality for many species for which no reliable direct estimates of survival are available.  In this paper, we evaluate the performance of regression models in predicting adult survival rates of birds from values of demographic and ecological covariates that are available from textbooks and databases.  We estimated adult survival for 67 species using dead recoveries of birds ringed in southern Africa and fitted regression models using five covariates: mean clutch size, mean body mass, mean age at first breeding, diet and migratoriness.  Models including these explanatory variables performed well in predicting adult survival in this set of species, both when phylogenetic relatedness of the species was taken into account using phylogenetic generalised least squares (51% of variation in logit survival explained) and when it was not (48%).  Two independent validation tests also indicated good predictive power, as indicated by high correlations of observed with expected values in a leave-one-out cross validation (LOOCV) test performed using data from the 67 species and when annual survival rates from independent mark–recapture studies of 38 southern African species were predicted from covariates and the regression using dead recoveries (LOOCV: 35% of variation in logit survival explained: mark-recapture estimates: 48%). Clutch size and body mass were the most influential covariates, both with and without the inclusion of phylogenetic effects, and a regression model including only these two variables performed well in both of the validation tests (LOOCV: 39% of variation in logit survival explained: mark-recapture estimates: 48%).  We conclude that our regression models, including the version with only clutch size and body mass, are likely to perform well in predicting adult survival rate for southern African species for which direct survival estimates are not available.

Habitat restoration is often recommended in conservation without first evaluating whether populations are in fact habitat limited and thus whether declining populations can be stabilized or recovered through habitat restoration. We used a spatially structured demographic model coupled with a dynamic neutral landscape model to evaluate whether habitat restoration could rescue populations of several generic migratory songbirds that differed in their sensitivity to habitat fragmentation (i.e., severity of edge effects on nesting success). Simulating a best-case scenario,  landscapes were instantly restored to 100% habitat before, at, or after habitat loss exceeded the species’ vulnerability threshold. The vulnerability threshold is a measure of extinction risk, in which the change in population growth rate (Δλ) scaled to the rate of habitat loss (Δh) falls below -1% (Δλ/Δh ≤ −0.01). Habitat restoration was most effective for species with low-to-moderate edge sensitivities and in landscapes that had not previously experienced extensive fragmentation. To stabilize populations of species that were highly edge sensitive or any species in heavily fragmented landscapes, restoration needed to be initiated long before the vulnerability threshold was reached. In practice, habitat restoration is generally not initiated until a population is at risk of extinction, but our model results demonstrate that some populations cannot be recovered at this point through habitat restoration alone. At this stage, habitat loss and fragmentation have seriously eroded the species’  demographic potential such that halting population declines is limited more by demographic factors than the amount of available habitat. Evidence that populations decline in response to habitat loss is thus not sufficient to conclude that habitat restoration will be sufficient to rescue declining populations.

Extensive habitat loss and changing agricultural practices have caused widespread declines in grassland birds throughout North America. The Flint Hills of Kansas and Oklahoma—the largest remaining tallgrass prairie—is important for grassland bird conservation despite supporting a major cattle industry. In 2004 and 2005, we assessed the community, population, and demographic responses of grassland birds to the predominant management practices (grazing, burning, and haying) of the region, including grasslands restored under the Conservation Reserve Program (CRP). We targeted 3 species at the core of this avian community: the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). Bird diversity was higher in native prairie hayfields and grazed pastures than CRP fields, which were dominated by Dickcissels. Although Dickcissel density was highest in CRP, their nest success was highest and nest parasitism by Brown-headed Cowbirds (Moluthrus ater) lowest in unburned hayfields (in 2004). Conversely, Grasshopper Sparrow density was highest in grazed pastures, but their nest success was lowest in these pastures and highest in burned hayfields, where cowbird parasitism was also lowest (in 2004). Management did not influence density and nest survival of Eastern Meadowlarks, which were uniformly low across the region. Nest success was extremely low (5–12%) for all 3 species in 2005, perhaps because of a record spring drought. Although the CRP has benefited grassland birds in agricultural landscapes, these areas may have lower habitat value in the context of native prairie. Hayfields may provide beneficial habitat for some grassland birds in the Flint Hills because they are mowed later in the breeding season than elsewhere in the Midwest. Widespread grazing and annual burning have homogenized habitat—and thus grassland-bird responses—across the Flint Hills. Diversification of management practices could increase habitat heterogeneity and enhance the conservation potential of the Flint Hills for grassland birds.

Observed rates of increase calculated from trends in the numbers of animals present in a population should generally agree with those estimated from life-history data. However, for a small population of individually identified sperm whales
Physeter macrocephalus occupying the waters of the eastern Caribbean there is a discrepancy. Using a mark-recapture analysis that included heterogeneity in identification, the population, numbering about 156 adults (95% CI 126−195) in 1998, has been increasing at 3.4% yr−1 (95% CI: 1.0−5.7% yr−1). However, a 2-stage matrix population model including unweaned calves and adults (and excluding mature males), whose parameters were estimated directly from empirical data, gave a projected rate of increase of −2.7% yr−1 (95% CI: −5.4 to −0.4% yr−1). This estimate is primarily sensitive to calculated adult mortality. The discrepancy between the  observed and projected rates of increase for this population may be explained by a high, probably anthropogenic, mortality of sperm whales in the eastern Caribbean, coupled with immigration from surrounding regions, so the area becomes an
attractive sink (ecological trap). The analysis emphasizes the fragility of sperm whale populations. More generally, our analysis of this population shows that a positive observed rate of increase is not necessarily a sign of a healthy population. This case study highlights the importance of analysing populations of endangered species using multiple  methodologies and with a solid base of individual-level empirical data based on longitudinal monitoring.