Although density-dependent processes and their impacts on population dynamics are key issues in ecology and conservation biology, empirical evidence of density-dependence remains scarce for species or populations with low densities, scattered distributions, and especially for managed populations where densities may vary as a result of extrinsic factors (such as harvesting or releases). Here, we explore the presence of density-dependent processes in a reinforced population of North African Houbara bustard (Chlamydotis undulata undulata). We investigated the relationship between reproductive success and local density, and the possible variation of this relationship according to habitat suitability using three independent datasets. Based on eight years of nests monitoring (more than 7000 nests), we modeled the Daily Nest Survival Rate (DNSR) as a proxy of reproductive success. Our results indicate that DNSR was negatively impacted by local densities and that this relationship was approximately constant in space and time: (1) although DNSR strongly decreased over the breeding season, the negative relationship between DNSR and density remained constant over the breeding season; (2) this density-dependent relationship did not vary with the quality of the habitat associated with the nest location. Previous studies have shown that the demographic parameters and population dynamics of the reinforced North African Houbara bustard are strongly influenced by extrinsic environmental and management parameters. Our study further indicates the existence of density-dependent regulation in a low-density, managed population.
Frost in late spring causes severe ecosystem damage in temperate and boreal regions. We here analyze late-spring frost occurrences between 1959 and 2017 and woody species’ resistance strategies to forecast forest vulnerability under climate change. Leaf-out phenology and leaf-freezing resistance data come from up to 1,500 species cultivated in common gardens. The greatest increase in leaf-damaging spring frost has occurred in Europe and East Asia, where species are more vulnerable to spring frost than in North America. The data imply that 35 and 26% of Europe’s and Asia’s forests are increasingly threatened by frost damage, while this is only true for 10% of North America. Phenological strategies that helped trees tolerate past frost frequencies will thus be increasingly mismatched to future conditions.
The goals of this study are to provide a map of actual habitat suitability (1), describe the relationships between abiotic predictors and the saguaro distribution at regional extents (2), and describe the potential effect of climate change on the spatial distribution of the saguaro (3).
Here we investigated the demographic history of the willow grouse (Lagopus lagopus), rock ptarmigan (Lagopus muta), and black grouse (Tetrao tetrix) through the Late Pleistocene using two complementary methods and whole genome data. Species distribution modeling (SDM) allowed us to estimate the total range size during the Last Interglacial (LIG) and Last Glacial Maximum (LGM) as well as to indicate potential population subdivisions.
Our results show that phylogenetically diverse assemblages with large phylogenetic age differences among species are associated with relatively high long‐term climate stability, with intra‐regional links between long‐term climate variability and phylogenetic composition especially strong in the more unstable regions. These findings point to future climate change as a key risk to the preservation of the phylogenetically diverse assemblages in regions characterized by relatively high paleoclimate stability, with China as a key example.
This paper [was highlighted in the *Editor's Picks* section of the Science Journal](https://www.dropbox.com/s/6k308eczv7i6kbj/2017_BMB_Journal_of_Biogeography_editors_choice.pdf?dl=1), and was among the [top downloaded articles](https://www.dropbox.com/s/sowq1h4bdngmipy/2017_BMB_Journal_of_Biogeography.png?dl=1) from the *Journal of Biogeography* during the 12 months after its publication.
Our results are inconsistent with the claim that climatic constraint and/or a lack of suitable habitats can fully explain the absence of Neanderthals in Southern Scandinavia during the Eemian Interglacial and Early Weichselian Glaciation. We do, however, find evidence that a geographic barrier may have impeded northerly migrations during the Eemian.
Intuitively, interannual spring temperature variability (STV) should influence the leaf‐out strategies of temperate zone woody species, with high winter chilling requirements in species from regions where spring warming varies greatly among years. We tested this hypothesis using experiments in 215 species and leaf‐out monitoring in 1585 species from East Asia (EA), Europe (EU) and North America (NA). The results reveal that species from regions with high STV indeed have higher winter chilling requirements, and, when grown under the same conditions, leaf out later than related species from regions with lower STV. Since 1900, STV has been consistently higher in NA than in EU and EA, and under experimentally short winter conditions NA species required 84% more spring warming for bud break, EU ones 49% and EA ones only 1%. These previously unknown continental‐scale differences in phenological strategies underscore the need for considering regional climate histories in global change models.
Our results do not support previous ideas about phenological strategies in temperate woody species (the ‘high temperature variability’ hypothesis; the ‘oceanic climate’ hypothesis; the ‘high latitude’ hypothesis). In regions with long winters, trees appear to rely on cues other than day length, such as winter chilling and spring warming. By contrast, in regions with short winters, some species—mostly from lineages with a warm-temperate or subtropical background, for example, Fagus additionally rely on photoperiodism. Therefore, photoperiod may be expected to constrain climate-driven shifts in spring leaf unfolding only at lower latitudes.
We had three key findings. First, dry forest is the least protected biome in Mesoamerica (4.5% protected), indicating that further action to safeguard this biome is warranted. Secondly, the poor overlap between protected areas and high-value forest conservation areas found herein may provide evidence that the establishment of protected areas may not be fully accounting for tree priority rank map. Third, high percentages of forest cover and high-value forest conservation areas still need to be represented by the protected areas network. Because deforestation rates are still increasing in this region, Mesoamerica needs funding and coordinated action by policy makers, national and local governmental and non-governmental organizations, conservationists and other stakeholders.