Wildlife Ecology and Conservation

Biodiversity hotspots for conservation priorities

Maximum entropy modeling of species geographic distributions

Modeling of species distributions with Maxent: new extensions and a comprehensive evaluation

Accurate modeling of geographic distributions of species is crucial to various applications in ecology and conservation. The best performing techniques often require some parameter tuning, which may be prohibitively time‐consuming to do separately for each species, or unreliable for small or biased datasets. Additionally, even with the abundance of good quality data, users interested in the application of species models need not have the statistical knowledge required for detailed tuning. In such cases, it is desirable to use “default settings”, tuned and validated on diverse datasets. Maxent is a recently introduced modeling technique, achieving high predictive accuracy and enjoying several additional attractive properties. The performance of Maxent is influenced by a moderate number of parameters. The first contribution of this paper is the empirical tuning of these parameters. Since many datasets lack information about species absence, we present a tuning method that uses presence‐only data. We evaluate our method on independently collected high‐quality presence‐absence data. In addition to tuning, we introduce several concepts that improve the predictive accuracy and running time of Maxent. We introduce “hinge features” that model more complex relationships in the training data; we describe a new logistic output format that gives an estimate of probability of presence; finally we explore “background sampling” strategies that cope with sample selection bias and decrease model‐building time. Our evaluation, based on a diverse dataset of 226 species from 6 regions, shows: 1) default settings tuned on presence‐only data achieve performance which is almost as good as if they had been tuned on the evaluation data itself; 2) hinge features substantially improve model performance; 3) logistic output improves model calibration, so that large differences in output values correspond better to large differences in suitability; 4) “target‐group” background sampling can give much better predictive performance than random background sampling; 5) random background sampling results in a dramatic decrease in running time, with no decrease in model performance.

Model selection in ecology and evolution

Fusion or Failure? The Future of Conservation Biology

The Social Structure and Reproductive Biology of Colonies of the Mole-Rat, Cryptomys damarensis (Rodentia, Bathyergidae)

Cryptomys damarensis occurs in semiarid regions of southwestern and central Africa. It lives in colonies in which reproduction is restricted to one or two of the largest-sized males and the largest female in the colony. Some division of labor, into frequent and infrequent workers, occurs within the remaining colony members. Reproduction and details of colony size and the number of breeding animals in a colony are described for two complete and five incomplete wild-captured colonies; one of the complete colonies and mole-rats from the incomplete colonies were maintained in captivity for more than 2 years. The breeding female initiated precopulatory behavior, mating occurred for about 2 weeks, the gestation length was 78–92 days, mean litter size was 2.8 (n = 10), and a maximum of four pups was born. The pups were precocial, wandered out of the nest within 24 h after birth, began to eat solids when 6 days old, and were fully weaned when 3 weeks old. When 6 weeks old, pups began to spar with each other and with some colony members, but levels of aggression were never high and the pups were incorporated into the colony. In the colony, subordinate and frequent-worker mole-rats weighed less than dominant animals and infrequent workers; mass, therefore, was not necessarily indicative of the age of the animal. During the 2-year study period, three mole-rats that were frequent workers on capture changed their castes to infrequent workers, two of them showed a concomitant increase in body mass. The colony structure and reproduction of C. damarensis are compared with those of the eusocial Heterocephalus glaber.

Reproductive biology of Australian acacias: important mediator of invasiveness?

Abstract Aim Reproductive traits are important mediators of establishment and spread of introduced species, both directly and through interactions with other life‐history traits and extrinsic factors. We identify features of the reproductive biology of Australian acacias associated with invasiveness. Location Global. Methods We reviewed the pollination biology, seed biology and alternative modes of reproduction of Australian acacias using primary literature, online searches and unpublished data. We used comparative analyses incorporating an Acacia phylogeny to test for associations between invasiveness and eight reproductive traits in a group of introduced and invasive (23) and non‐invasive (129) species. We also explore the distribution of groups of trait ‘syndromes’ between invasive and non‐invasive species. Results Reproductive trait data were only available for 126 of 152 introduced species in our data set, representing 23/23 invasive and 103/129 non‐invasive species. These data suggest that invasives reach reproductive maturity earlier (10/13 within 2 years vs. 7/26 for non‐invasives) and are more commonly able to resprout (11/21 vs. 13/54), although only time to reproductive maturity was significant when phylogenetic relationships were controlled for. Our qualitative survey of the literature suggests that invasive species in general tend to have generalist pollination systems, prolific seed production, efficient seed dispersal and the accumulation of large and persistent seed banks that often have fire‐, heat‐ or disturbance‐triggered germination cues. Conclusions Invasive species respond quicker to disturbance than non‐invasive taxa. Traits found to be significant in our study require more in‐depth analysis involving data for a broader array of species given how little is known of the reproductive biology of so many taxa in this species‐rich genus. Sets of reproductive traits characteristic of invasive species and a general ability to reproduce effectively in new locations are widespread in Australian acacias. Unless there is substantial evidence to the contrary, care should be taken with all introductions.