Vertebrate Ecology

The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.

Morphological approaches have been used extensively to understand assembly rules (species in-
teractions, environmental filtering, and neutral processes) that structure ecological communities. Desert
anurans cope with limited water by either being restricted to permanent water or becoming more
fossorial, which should be reflected in their morphology. We examined morphological diversity of 16 frog
species across six habitat types within the Chihuahuan Desert to investigate the relationship between
species richness and morphological space. We measured 13 morphological traits associated with loco-
motion, habitat use, and feeding. Principal components analysis separated species into three ecomor-
phological groups: fossorial, terrestrial, and semi-aquatic species. Morphological diversity was analyzed
and compared against a null model and revealed nonrandom community structure. The total assemblage
morphospace increased in relation to species richness, though this relationship was not significant.
Species were significantly packed within the morphospace exhibiting high morphological similarity
while being less evenly dispersed, with increasing species richness, indicative of a response to an
environmental gradient. Given the highly xeric nature of the Chihuahuan Desert, our results support the
assumption that environmental filtering, rather than interspecific interactions, shapes assemblages'
structure by favoring species with similar traits to co-occur more often within a given habitat type than
expected by chance.

The impact of alien predators on native prey populations is often attributed to prey naiveté towards a novel threat. Yet evolutionary theory predicts that alien predators cannot remain eternally novel; prey species must either become extinct or learn and adapt to the new threat. As local enemies lose their naiveté and coexistence becomes possible, an introduced species must eventually become ‘native’. But when exactly does an alien become a native species? The dingo (Canis lupus dingo) was introduced to Australia about 4000 years ago, yet its native status remains disputed. To determine whether a vulnerable native mammal (Perameles nasuta) recognizes the close relative of the dingo, the domestic dog (Canis lupus familiaris), we surveyed local residents to determine levels of bandicoot visitation to yards with and without resident dogs. Bandicoots in this area regularly emerge from bushland to forage in residential yards at night, leaving behind tell-tale deep, conical diggings in lawns and garden beds. These diggings were less likely to appear at all, and appeared less frequently and in smaller quantities in yards with dogs than in yards with either resident cats (Felis catus) or no pets. Most dogs were kept indoors at night, meaning that bandicoots were not simply chased out of the yards or killed before they could leave diggings, but rather they recognized the threat posed by dogs and avoided those yards. Native Australian mammals have had thousands of years experience with wild dingoes, which are very closely related to domestic dogs. Our study suggests that these bandicoots may no longer be naïve towards dogs. We argue that the logical criterion for determining native status of a long-term alien species must be once its native enemies are no longer naïve.

Sundarbans (Bangladesh) mangrove forest is the largest contiguous mangrove ecosystem in the world. At 10,000 square km, it is also the largest wetland ecosystem with international importance for waterfowl habitats. The Bengal tiger (Panthera tigris tigris) is a focal species for biodiversity conservation management in the Sundarbans. Conservationists claim that Sundarbans harbors the largest population of tigers in south Asia. Sundarbans also acquired national and international protected area classifications; 23% of its total area has been designated as Sundarbans Wildlife Sanctuaries and United Nations World Heritage Sites. Use of the tiger as a keystone species and its impact on socioecological and economic considerations needs to be reviewed critically with the aim of formulating a management action plan for tiger conservation in the region.