Jorge Soberón

Future projections for Mexican faunas under global climate change scenarios

Global climates are changing rapidly, with unexpected consequences. Because elements of biodiversity respond intimately to climate as an important driving force of distributional limitation, distributional shifts and biodiversity losses are expected. Nevertheless, in spite of modelling efforts focused on single species or entire ecosystems, a few preliminary surveys of fauna-wide effects, and evidence of climate change-mediated shifts in several species, the likely effects of climate change on species distributions remain little known, and fauna-wide or community-level effects are almost completely unexplored. Here, using a genetic algorithm and museum specimen occurrence data, we develop ecological niche models for 1,870 species occurring in Mexico and project them onto two climate surfaces modelled for 2055. Although extinctions and drastic range reductions are predicted to be relatively few, species turnover in some local communities is predicted to be high (>40% of species), suggesting that severe ecological perturbations may result.

Effects of global climate change on geographic distributions of Mexican Cracidae

Although climate change and its implications are a frequent subject of detailed study, the effects of these changes on species’ geographic distributions remain little explored. We present a first cross-species analysis of the effects of global climate change on the distributions of one bird family, the Cracidae, in Mexico, based on projecting models of ecological niches from present conditions to modeled future conditions taken from general circulation models of climate change. Based on two different scenarios of climate change and on three assumptions regarding species’ dispersal abilities, effects on species’ distributions range from drastic reduction to modest increases. These results illustrate the complex nature of species’ geographic responses to environmental change, and emphasize the need for detailed analysis of individual species’ ecological requirements.

The use of specimen-label databases for conservation purposes: an example using Mexican Papilionid and Pierid butterflies

In recent years, use of databases of the labels of specimens deposited in museums and herbaria is becoming increasingly common as a tool for addressing biodiversity conservation and management problems. These databases are often large in size and complex in structure, and their application to conservation deserves a wider appreciation of some of the biases, gaps and potential pitfalls common to them. In this paper, we discuss some of the problems associated with using such databases for obtaining lists of species for arbitrary sites, as well as for the estimation of the distribution area of single species. The possibility of obtaining these closely related variables using specimen databases is shown to be scale-dependent. A tool based on mark-recapture techniques is applied to the problem of: (i) detecting sites with low number of species due to lack of adequate in-site sampling and, (ii) species with small estimated areas due to poor spatial coverage of samples.

The dynamics of a plant-pollinator interaction

Abstract A mathematical model of the dynamics of plant-pollinator interaction is presented. The functional response of individual pollinators to the density of plants is considered and this makes possible the existence of two equilibrium points for the association. The stability analysis is framed in terms of two parameters of the model: the nectar rewards which the plant offers the pollinator and the specificity of the pollinator to the plant. The main results are: (a) there is an optimum level of nectar production which maximises the plant birth rate; (b) increasing nectar production and/or decreasing pollinator specificity produce more stable associations; (c) for highly specific pollinators a conflict arises between stability of association and optimality in nectar production.

Non-resource based territoriality in males of the butterfly Xamia xami (Lepidoptera: Lycaenidae)

In the Pedregal de San Angel reserve, in Mexico City, males of the butterfly Xamia xamiperch in and defend areas with well-defined topographic limits. These areas lack concentrations of receptive females and of larvae and adult resources. One individual defends the same territory an average of 5 h/day, up to a maximum of 23 days. The same areas are used as territories by different males during the year. These areas share some characteristic features which are described. Evidence is presented in support of the hypothesis that the territories function as mating stations. A possible scenario for the evolution of this territorial mating system is advanced.

Prediction of potential areas of species distributions based on presence-only data

We introduce a methodology to infer zones of high potential for the habitat of a species, useful for management of biodiversity, conservation, biogeography, ecology, or sustainable use. Inference is based on a set of sites where the presence of the species has been reported. Each site is associated with covariate values, measured on discrete scales. We compute the predictive probability that the species is present at each node of a regular grid. Possible spatial bias for sites of presence is accounted for. Since the resulting posterior distribution does not have a closed form, a Markov chain Monte Carlo (MCMC) algorithm is implemented. However, we also describe an approximation to the posterior distribution, which avoids MCMC. Relevant features of the approach are that specific notions of data acquisition such as sampling intensity and detectability are accounted for, and that available a priori information regarding areas of distribution of the species is incorporated in a clear-cut way. These concepts, arising in the presence-only context, are not addressed in alternative methods. We also consider an uncertainty map, which measures the variability for the predictive probability at each node on the grid. A simulation study is carried out to test and compare our approach with other standard methods. Two case studies are also presented.

Morphological grouping of Mexican butterfliesin relation to habitat association

Current rates of destruction of natural ecosystems call for rapid and efficient ways of assessing the successional state or degree of perturbation, and of monitoring management efforts. In this paper we propose that butterfly species, grouped by morphological and ethological traits, can be used for these purposes. The groups, each composed of species from many taxa, appear to be strongly correlated with types of habitat. We re-define the groups originally distinguished by de la Maza and de la Maza (1988), and, using data from Quintana Roo and Morelos states in Mexico, show a statistical association between certain coloration groups and types of habitat. The existence of such consistent, non-taxonomic groupings is of theoretical interest and may also be used to monitor habitats or to predict the effects of disturbance.

Population dynamics of a Rhizobium-legume interaction. A mathematical model

A model of the mutualistic interaction between Legumes and Rhizobium bacteriae is presented. Using the statistical distribution of active nodules in the plant population, the demographic benefits that plants with i nodules possess can be integrated to obtain the benefit for the population as a whole. The effects of the parameters in the plant population size is studied numerically. These effects are strongly influenced by the degree of aggregation of the distribution of active nodules.

PRELIMINARY ANALYSIS OF THE ECOLOGY AND GEOGRAPHY OF THE ASIAN NUTHATCHES (AVES: SITTIDAE)

Abstract We explored distributions of Asian nuthatch species in ecological and geographic space using ecological niche modeling based on occurrence data associated with specimens and observations. Nuthatches represent a well-defined clade occurring throughout the Northern Hemisphere, but are most diverse in southern Asia where 15 of the 24 species occur and where the lineage is believed to have evolved. Species richness was focused in a narrow east–west band corresponding to the forested parts of the Himalayas with a maximum number of nine species predicted present in these foci. The distributional predictions have a mid-elevation focus with highest species diversity between 1,000 and 2,000 m. Niche breadth and volume were positively related, but accumulation of distributional area (niche volume) decreased with additional environmental combinations (niche breadth). The extent of potential range filling, a measure of distributional disequilibrium, was connected with montane habit (R2 = 0.422) indicating that montane situations limit the distributional potential of species.