Species distribution modeling (SDM) is an increasingly important tool to predict the geographic distribution of species. Even though many problems associated with this method have been highlighted ...and solutions have been proposed, little has been done to increase comparability among studies. We reviewed recent publications applying SDMs and found that seventy nine percent failed to report methods that ensure comparability among studies, such as disclosing the maximum probability range produced by the models and reporting on the number of species occurrences used. We modeled six species of Falco from northern Europe and demonstrate that model results are altered by (1) spatial bias in species' occurrence data, (2) differences in the geographic extent of the environmental data, and (3) the effects of transformation of model output to presence/absence data when applying thresholds. Depending on the modeling decisions, forecasts of the future geographic distribution of Falco ranged from range contraction in 80% of the species to no net loss in any species, with the best model predicting no net loss of habitat in Northern Europe. The fact that predictions of range changes in response to climate change in published studies may be influenced by decisions in the modeling process seriously hampers the possibility of making sound management recommendations. Thus, each of the decisions made in generating SDMs should be reported and evaluated to ensure conclusions and policies are based on the biology and ecology of the species being modeled.
We reviewed published phylogenies and selected 111 phylogenetic studies representing mammals, birds, insects, and flowering plants. We then mapped the latitudinal range of all taxa to test the ...relative importance of the tropical conservatism, out of the tropics, and diversification rate hypotheses in generating latitudinal diversity gradients. Most clades originated in the tropics, with diversity peaking in the zone of origin. Transitions of lineages between latitudinal zones occurred at 16–22% of the tree nodes. The most common type of transition was range expansions of tropical lineages to encompass also temperate latitudes. Thus, adaptation to new climatic conditions may not represent a major obstacle for many clades. These results contradict predictions of the tropical conservatism hypothesis (i.e., few clades colonizing extratropical latitudes), but support the out-of-the-tropics model (i.e., tropical originations and subsequent latitudinal range expansions). Our results suggest no difference in diversification between tropical and temperate sister lineages; thus, diversity of tropical clades was not explained by higher diversification rates in this zone. Moreover, lineages with latitudinal stasis diversified more compared to sister lineages entering a new latitudinal zone. This preserved preexisting diversity differences between latitudinal zones and can be considered a new mechanism for why diversity tends to peak in the zone of origin.
Abstract The effect of non‐native herbivores on ecosystems and diversity has become a global concern in conservation. Management challenges associated with non‐native free‐roaming equids have existed ...for decades in a wide range of ecosystems yet have been difficult to resolve. Although much of the challenge is associated with non‐biological considerations, empirical ecological research is crucial for guiding sound management decisions. We conducted a field study on the associations between feral burros ( Equus asinus ) and elements of the Sonoran Desert ecosystem in Arizona, USA, during 2017–2019. We identified areas with and without established burro herds, and collected data on vegetation, ungulate sign, small mammals, birds, and herpetofauna at multiple, randomly selected grids within these areas, while accounting for vegetation community and distance to water. We predicted that burros would be associated with differences in vegetation metrics such as lower ground cover, smaller perennial plant size, and lower plant density, foliage density, recruitment, and species richness among perennial native plants susceptible to burro foraging or trampling. We further predicted that these differences would be accompanied by lower density or relative abundance and lower species richness of small mammals, birds, and herpetofauna. Finally, because burro distribution has been documented to be associated with water in this arid landscape, we predicted that effects would be most pronounced near water. The results of our study did not consistently support our predictions, perhaps because of small sample sizes or, in several cases, inherent complexities associated with seasonal burro habitat use and plant phenology patterns. However, our study documented that the presence of this feral equid is associated with a number of key differences that may be ecologically important and have the potential to alter community structure in this sensitive arid ecosystem. In areas with established burro herds, we documented lower ground cover, plant density, foliage density, or smaller plant size in several species, and changes were often influenced by distance from water. For example, density of Engelmann's prickly pear cactus ( Opuntia engelmannii ) was 94% lower and Anderson wolfberry ( Lycium andersonii ) plants were 49% smaller in areas with established burro herds. In areas with burros, we also recorded lower density of white bursage ( Ambrosia dumosa ) in areas distant from water. Of notable concern was that our metric of recruitment indicated 63% lower recruitment in saguaro cactus ( Carnegiea gigantea ) and that foliage densities of yellow paloverde ( Parkinsonia microphylla ) and desert ironwood ( Olneya tesota ) were lower in areas with established burro herds. Data on some plant species did not support our predictions. For example, white bursage and Anderson wolfberry plants were found at similar densities in areas with and without established burros near water, but they occurred at lower densities far from water in areas with established burros. Our data revealed that in 4 of 7 small mammal species evaluated (Bailey's pocket mouse Chaetodipus baileyi , desert pocket mouse C. penicillatus , deer mice Peromyscus spp., and Merriam's kangaroo rat Dipodomys merriami ), density was associated with an interaction between burros and distance to water, with lower densities close to water in burro areas. Contrary to predictions, 3 of these species (Bailey's pocket mouse, desert pocket mouse, and deer mice) exhibited higher densities in burro areas than in non‐burro areas at grids farther from water. Density of a fifth species (Arizona woodrat Neotoma devia ) was 68% lower in burro areas than in non‐burro areas, and the densities of 2 species were not associated with burros. Across species, we did not find consistent patterns in our analysis of bird group density, with some species exhibiting a negative effect associated with burros and others exhibiting a positive effect. When we categorized birds by hypothesized nesting and foraging vulnerabilities (low, medium, high), vulnerability levels did not predict the effect of burros. However, all categories exhibited a negative burro effect distant from water but not close to water, contrary to our expectations. Relative abundance of common side‐blotched lizards ( Uta stansburiana ) was 26% lower in areas with established burros, but data on other herpetofauna species did not support our predictions, with some species exhibiting higher relative abundance in areas with established burros. Our data did not reveal an association between burros and bird, small mammal, or herpetofauna species richness, but species richness of native perennial plants was higher in burro areas close to water. We recommend that future bird studies focus on riparian birds and nest success, and possibly evaluate potential effects in relation to other aspects of bird ecology such as feeding guilds or nesting ecology, and that future herpetofauna studies use survey methods that can better account for detection. Although some results did not support our predictions, our study documented negative associations between burros and a number of native plant species, and density in some small mammal species. These associations are important and of concern in and of themselves because changes in long‐lived keystone plant species and in small mammal densities indicate that the long‐term sustainability of portions of this ecosystem may be affected, and it is likely that these changes can have additional indirect effects on plants and wildlife in this ecosystem. Field data on ungulate sign (fecal groups and tracks) suggested that the associations detected in our study were related to burros and not cattle ( Bos taurus ) or native ungulates such as mule deer ( Odocoileus hemionus ) or bighorn sheep ( Ovis canadensis ). Our results indicate that the presence of established burro herds was associated with changes, primarily in the plant community that is critical for ecosystem function, and we suggest that current management of this feral equid may not be adequate for maintaining the long‐term viability of this arid and fragile ecosystem.
Asociaciones Entre un Equino Salvaje y el Ecosistema del Desierto Sonorense Resumen El efecto de los herbívoros no nativos sobre los ecosistemas y la diversidad se ha convertido en una preocupación mundial en materia de conservación. Los desafíos de gestión asociados con los équidos no nativos en libertad han existido durante décadas en una amplia gama de ecosistemas, pero han sido difíciles de resolver. Aunque gran parte del desafío está asociado con consideraciones no biológicas, la investigación ecológica empírica es crucial para guiar decisiones de gestión acertadas. Realizamos un estudio de campo sobre las asociaciones entre los asnos o burros salvajes ( Equus asinus ) y elementos del ecosistema del Desierto Sonorense en Arizona, EE. UU., durante 2017‐2019. Identificamos áreas con y sin manadas de burros establecidas, y recopilamos datos sobre vegetación, signos de ungulados, pequeños mamíferos, aves y herpetofauna en múltiples cuadrículas seleccionadas al azar dentro de estas áreas, teniendo en cuenta la asociación de la vegetación y la distancia al agua. Predijimos que los burros estarían asociados con diferencias en las métricas de la vegetación, como una menor cobertura del suelo, un tamaño más pequeño de las plantas perenes y una menor densidad de plantas, densidad de follaje, reclutamiento y riqueza de especies entre las plantas nativas perenes susceptibles a la búsqueda de alimento o al pisoteo de los burros. Además, predijimos que estas diferencias estarían acompañadas de una menor densidad o abundancia relativa y una menor riqueza de especies de pequeños mamíferos, aves y herpetofauna. Finalmente, debido a que se ha documentado que la distribución de los burros está asociada con el agua en este paisaje árido, predijimos que los efectos serían más pronunciados cerca del agua. Los resultados de nuestro estudio no respaldaron consistentemente nuestras predicciones, tal vez debido a tamaños de muestra pequeños o, en varios casos, complejidades inherentes asociadas con el uso estacional del hábitat de los burros y los patrones de fenología de las plantas. Sin embargo, nuestro estudio documentó que la presencia de este équido salvaje está asociada con una serie de diferencias clave que pueden ser ecológicamente importantes y tienen el potencial de alterar la estructura de la comunidad de este sensible ecosistema árido. En áreas con manadas de burros establecidas, documentamos una menor cobertura del suelo, densidad de plantas, densidad de follaje o menor tamaño de plantas en varias especies, y los cambios a menudo estuvieron influenciados por la distancia al agua. Por ejemplo, la densidad del nopal cuijo ( Opuntia engelmannii ) era un 94% menor y las plantas de frutilla ( Lycium andersonii ) eran un 49% más pequeñas en áreas con manadas de burros establecidas. En áreas con burros, también registramos menor densidad de hierba del burro ( Ambrosia dumosa ) en áreas alejadas del agua. Fue de notable preocupación que nuestra métrica de reclutamiento indicó un reclutamiento 63% menor en cactus saguaro ( Carnegiea gigantea ) y que las densidades de follaje de paloverde amarillo ( Parkinsonia microphylla ) y palo fierro ( Olneya tesota ) fueron menores en áreas con manadas de burros establecidas. Los datos sobre algunas especies de plantas no respaldaron nuestras predicciones. Por ejemplo, las plantas de hierba de burro y frutilla se encontraron en densidades similares en áreas con y sin burros establecidos cerca del agua, pero ocurrieron en densidades más bajas lejos del agua en áreas con burros establecidos. Nuestros datos revelaron que en 4 de 7 especies de pequeños mamíferos evaluadas (ratón de Abazones Sonorense Chaetodipus baileyi , ratón de Abazones del desierto C. penicill
Mexican wolf recovery planning has spanned >3 decades, yet federal and state planners have not reached consensus on how to structure recovery efforts with the remaining inbred founder lineages to ...maximize genetic diversity while balancing many other demographic and social considerations. The US Fish and Wildlife Service and state wildlife agencies are working to draft a revised recovery plan specific to the Mexican wolf that will appropriately incorporate genetic concerns in recovery criteria that can be implemented on a human-dominated landscape. Inbreeding effects, where present in the remaining lineages, are stochastic and unpredictable in a management context. Despite these effects, population growth in Mexican wolves the past 5years rivals the rate observed in Yellowstone wolves during the last decade. While small populations risk extinction via inbreeding depression, there are often larger, more imminent threats of demographics, mortality, or habitat loss that may impact success of recovery efforts. Releasing captive-reared wolves is problematic and often creates conflict in local human communities, but fostering of captive-born wolves into wild wolf packs is a viable means of increasing genetic diversity and decreasing habituated wolf-human conflict. There are many alternative ways to estimate the number of wolves per population needed to recover the Mexican wolf. Efforts should thus be made to provide for sufficient genetic diversity, but not at the expense of more immediate factors that influence successful recovery.
•Genetic considerations for recovery planning in Mexican wolves are discussed.•Genetic goals must be balanced against immediate biological and social challenges.•Captive wolves released to wild added little genetic material to wild population.•There is no single number that determines whether a population is recovered.•PVA absolute extinction probabilities do not discount alternative recovery actions.
The Wallow Fire, the largest wildfire in Arizona history, encompassed 2,170 km2 and provided a rare opportunity to examine habitat selection and home ranges of American black bears (Ursus americanus) ...before and after a wildfire. We had fitted global positioning system (GPS) collars on 47 bears from 2005 to April 2011, and 10 of these were still collared when the fire started in May 2011. We captured and collared an additional 7 black bears within the fire perimeter post‐fire (Jul–Sep 2011 and Jun 2012). To evaluate how black bears were affected by the fire, we fit a step selection function using a conditional mixed effects Poisson regression model to estimate the relative strength of black bear habitat selection in response to burn severity. Additionally, we estimated home range sizes using an autocorrelated kernel density estimator by means of a continuous‐time movement model. We then used a generalized linear model with a negative binomial error distribution and mixed effects to estimate the effect of the burn severity on black bear home range size, while controlling for sex and drought. In spring and summer in years prior to the fire, bears selected areas that later burned in the fire. After the fire, bears used all burn severities, but their selection for high‐severity burns decreased significantly in summer 2011 and fall 2012. Home range sizes were 3.06 times larger pre‐fire than post‐fire. Our study demonstrates that black bears continued to use all burn severities after a major wildfire, and that post‐fire conditions did not result in expanded black bear home ranges.
Following the largest wildfire in Arizona history, black bears selected unburned and lower severity burned areas, though season had a significant effect on selection of burn severity classes. Black bear home ranges were larger pre‐ than post‐fire.
Bighorn sheep (Ovis canadensis) evolved for thousands of years in the presence of numerous predators, including mountain lions (Puma concolor). Bighorn sheep have presumably developed predator ...avoidance strategies; however, the effectiveness of these strategies in reducing risk of mountain lion predation is not well understood. These strategies are of increasing interest because mountain lion predation on bighorn sheep has been identified as a leading cause of mortality in some sheep populations. Therefore, we investigated how mountain lions affect both bighorn sheep habitat selection and risk of mortality in Arizona, USA. We used 2 approaches to investigate the predator‐prey relationship between mountain lions and bighorn sheep. We fit 103 bighorn sheep (81 females and 22 males) with global positioning system radio‐collars in 2 Arizona populations from 2013 to 2017, and used a negative binomial resource selection probability function to evaluate whether bighorn sheep selected for habitat features in accordance with presumed predator avoidance strategies, including terrain ruggedness, slope, topographic position, and horizontal obstruction, in 2 seasons (winter and summer). We then estimated how habitat features such as terrain ruggedness, slope, horizontal obstruction, and group size, influence the risk of mortality due to mountain lion predation using an Andersen‐Gill proportional hazards model. Generally, both sexes selected areas with lower horizontal obstruction and intermediate ruggedness and slope, but selection patterns differed between seasons and sexes. The use of more rugged areas and steeper slopes decreased the risk of mortality due to mountain lion predation, consistent with presumed predator avoidance strategies. Increased group size decreased risk of bighorn sheep mortality due to mountain lion predation but this effect became marginal at approximately 10 individuals/group. We did not identify a relationship between horizontal obstruction and bighorn sheep mortality risk. Our findings can be used in habitat and population management decisions such as the prioritization of habitat restoration sites or selection of translocation sites. In addition, we suggest that augmentation of low‐density bighorn sheep populations may reduce mountain lion predation risk by increasing group size, and that releasing large groups of bighorn sheep in population augmentation and reintroduction efforts may help to reduce mountain lion predation.
Bighorn sheep selected for areas with decreased horizontal obstruction and areas of intermediate slope and ruggedness. Ruggedness, steep slopes, and increased bighorn sheep group size decrease the risk of bighorn sheep mortality due to mountain lion predation. We suggest that habitat manipulations, such as prescribed fire, and translocating larger groups of bighorn sheep may increase the amount of available bighorn sheep habitat and decrease the risk of bighorn sheep mortality due to mountain lion predation, respectively.
The phylogeography of the American black bear (Ursus americanus) is characterized by isolation into glacial refugia, followed by population expansion and genetic admixture. Anthropogenic activities, ...including overharvest, habitat loss, and transportation infrastructure, have also influenced their landscape genetic structure. We describe the genetic structure of the American black bear in the American Southwest and northern Mexico and investigate how prehistoric and contemporary forces shaped genetic structure and influenced gene flow. Using a suite of microsatellites and a sample of 550 bears, we identified 14 subpopulations organized hierarchically following the distribution of ecoregions and mountain ranges containing black bear habitat. The pattern of subdivision we observed is more likely a product of postglacial habitat fragmentation during the Pleistocene and Holocene, rather than a consequence of contemporary anthropogenic barriers to movement during the Anthropocene. We used linear mixed‐effects models to quantify the relationship between landscape resistance and genetic distance among individuals, which indicated that both isolation by resistance and geographic distance govern gene flow. Gene flow was highest among subpopulations occupying large tracts of contiguous habitat, was reduced among subpopulations in the Madrean Sky Island Archipelago, where montane habitat exists within a lowland matrix of arid lands, and was essentially nonexistent between two isolated subpopulations. We found significant asymmetric gene flow supporting the hypothesis that bears expanded northward from a Pleistocene refugium located in the American Southwest and northern Mexico and that major highways were not yet affecting gene flow. The potential vulnerability of the species to climate change, transportation infrastructure, and the US–Mexico border wall highlights conservation challenges and opportunities for binational collaboration.
The pattern of subdivision among black bears in the Southwest is more likely a product of postglacial habitat fragmentation during the Pleistocene and Holocene rather than a consequence of contemporary anthropogenic barriers to movement during the Anthropocene. We found significant asymmetric gene flow supporting the hypothesis that bears expanded northward from a Pleistocene refugium located in the American Southwest and northern Mexico and that major highways were not yet affecting gene flow. The potential vulnerability of the species to climate change, transportation infrastructure, and the U.S.‐Mexico border wall highlights conservation challenges and opportunities for binational collaboration.
Evolution of Maximum Body Size of Terrestrial Mammals Smith, Felisa A; Boyer, Alison G; Brown, James H ...
Science (American Association for the Advancement of Science),
11/2010, Letnik:
330, Številka:
6008
Journal Article
Recenzirano
The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of ...maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant. There was remarkable congruence in the rate, trajectory, and upper limit across continents, orders, and trophic guilds, despite differences in geological and climatic history, turnover of lineages, and ecological variation. Our analysis suggests that although the primary driver for the evolution of giant mammals was diversification to fill ecological niches, environmental temperature and land area may have ultimately constrained the maximum size achieved.
The American mink’s relationship to the weasels in
Mustela has been uncertain. Karyological, morphological, and phylogenetic comparisons to Eurasian
Mustela support placing the mink outside the genus ...as
Neovison vison. However, genetic comparisons that incorporate other endemic American
Mustela suggest the interpretation of
N. vison’s position to
Mustela has been handicapped by biased geographic sampling. Here, we analyzed mitochondrial cytochrome-
b from all weasels endemic to the Americas, including two poorly known South American species (
M. felipei,
M. africana), weasels native to North America (
M. vison,
M. frenata,
M. nigripes),
Mustela migrant to North America (
M. erminea,
M. nivalis), palearctic
Mustela, and other American members of Mustelidae. Bayesian and likelihood inference methods were used to construct a phylogeny of
Mustela, and relaxed Bayesian phylogenetic techniques estimated ages of divergence within the genus using priors calibrated by fossil ages. Our analyses show that the American mink and the smaller
Mustela endemic to the Americas represent a distinct phylogenetic heritage apart from their Eurasian cousins, and biogeographic barriers like the Bering and Panamanian land bridges have influenced the evolutionary history of
Mustela in the Americas.
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