Early performance of two tropical dry forest species after assisted migration to pine-oak forests at different altitudes:strategic response to climate change

Assisted migration has been proposed as a strategy for adaptive management of forest species in response to expected effects of climate change,but it is controversial for several reasons.Tropical dry forests are among the most threatened ecosystems in the world.In Mexico,historically,land-use change and deforestation have been decreasing forest cover,and climate change is shifting the potential distribution of different forest types,exacerbating the risk of local extinctions.Assisted altitudinal migration could be a feasible strategy for reducing local extinctions in response to climate change and lack of landscape connectivity.Our objective was to evaluate survival and growth of Albizia plurijuga and Ceiba aesculifolia,two tropical deciduous forests species in Mexico.We transplanted 4-month-old seedlings to experimental raised beds at three altitudes(2100,2400 and 2700 m a.s.l.),exceeding their upper regional limit of distribution(2000 m a.s.l.).We also tested seed germination at each altitude.We monitored the experiment for 10 months.For both species,as altitude increased and cold weather was more prevalent,plant performance declined.Within species,differences in individual growth were significant among altitudes.Overall survival was 18.5%for A.plurijuga and 24.5%for C.aesculifolia.Both species had higher survival and better growth at lower altitude,and no seedling emergence at any altitude.We conclude that assisted migration can be implemented for each species by an upward attitudinal shift within,and not exceeding,400 m beyond their present upper altitudinal limit of distribution.Our results indicate that for many species that show altitudinal gradients at regional scales,unless current climate conditions change,the potential to establish outside their range is minimal.

Demographic and behavioral responses of the White-winged Dove to human disturbances during winter in northwestern Mexico

The simultaneous study of demography and behavior might provide a more comprehensive understanding about animal responses to anthropogenic disturbances.The White-winged Dove(Zenaida asiatica)is a frequent dweller of urban and agricultural habitats in North America,Central America,and the Caribbean.Still,research on the species is heavily biased to the USA.We analyzed the response of the species to human disturbances during winter across an urban-agricultural landscape in northwestern Mexico through a demographic and behavioral approach.We modeled the effect of disturbance types(pedestrians,cars,pavement and building cover)on the density of the species.Also,we investigated if surveillance behavior varied across the landscape by estimating and comparing perching proportion among land uses(urban grey areas,urban green areas,cropfields,shrublands).We did not detect the species within cropfields,possibly because food resources were not available for the dove during winter in this land use.Pavement cover limited species’density,as it might reduce the surface of the preferred feeding substrates of the dove.Pedestrians and building cover increased the density of the species,as they might provide food and shelter for the dove,respectively.Surveillance behavior peaked in urban grey areas,whereas it dropped in urban green areas.Differences on threat levels,threat type,and protective cover among land uses might in-fluence such behavioral pattern.Our approach contributes to the knowledge of the species and demonstrates that both demographic and behavioral cues provide complementary evidence for analyzing the impact of human disturbances on animals.

Amphibian richness along modified riparian areas of central Mexico:conservation priorities

Background:Land‑use change frequently affects faunistic populations and communities.To achieve successful conservation strategies,we need suitable information about species distribution and the causes of extinction risk.Many amphibian species depend on riparian vegetation to complete their life cycles.About 41%of amphibian species are globally threatened,and accurate estimations of population size,species richness and the identification of critical habitats are urgently needed worldwide.To evaluate the magnitude of changes in species richness and demography,estimations that include detection probability are necessary.In this study,we employed multi‑species occupancy models to estimate detection probability and the effect of land cover type(i.e.,cropland,artificial pasture,secondary and mature forest)in a 500‑m radius on the occupancy probability and richness of diurnal amphibians in 60 riparian zones in the state of Michoacán in central Mexico.Furthermore,we evaluated the potential of the endemic salamander Ambystoma ordinarium as a flagship species for the conservation of other native amphibian species.Results:We registered a total of 20 amphibian species in the diurnal assemblage,of which 10 species are considered at risk of extinction.We found that cropland was the most important land‑use type for explaining amphibian distribu‑tion in riparian zones,with negative effects on most amphibian species.We found no differences in species richness between zones with and without A.ordinarium.In riparian zones occupied by A.ordinarium,however,we found a higher number of species at risk of extinction.Conclusions:Our findings showed negative effects of croplands on the distribution of most amphibian species.The riparian zones are important for the maintenance of native diurnal amphibian communities and A.ordinarium can act as a flagship species for the conservation of threatened amphibian species.