Claude Gascon

Global Biodiversity Conservation: The Critical Role of Hotspots

Global changes, from habitat loss and invasive species to anthropogenic climate change, have initiated the sixth great mass extinction event in Earth’s history. As species become threatened and vanish, so too do the broader ecosystems and myriad benefits to human well-being that depend upon biodiversity. Bringing an end to global biodiversity loss requires that limited available resources be guided to those regions that need it most. The biodiversity hotspots do this based on the conservation planning principles of irreplaceability and vulnerability. Here, we review the development of the hotspots over the past two decades and present an analysis of their biodiversity, updated to the current set of 35 regions. We then discuss past and future efforts needed to conserve them, sustaining their fundamental role both as the home of a substantial fraction of global biodiversity and as the ultimate source of many ecosystem services upon which humanity depends.

Population‐ and Community‐Level Analyses of Species Occurrences of Central Amazonian Rainforest Tadpoles

In this paper I examine occurrence patterns and habitat use of a New World tropical tadpole species assemblage from primary tropical terra firme forest. First, I describe phenology of reproduction. I then undertake a population approach to examine abiotic characteristics associated with sites used for reproduction by each species. Finally, analysis at a more general level tests to see if some correlative structure exists at the community level, i.e., do sites with similar tadpole species also have similar abiotic characteristics? A significant correlation would indicate, for example, that sites with similar abiotic charac- teristics also share species assemblages. Fifty-three independent aquatic sites were sampled across two consecutive rainy seasons (two 9-mo periods). Twenty-five tadpole species were encountered during the entire study. Significant differences existed among four types of habitats (terra firme pools, peccary wallows, streamside pools, and streams), all located within primary undisturbed forest, with respect to abiotic characteristics such as site permanency and mean depth of water. Most of the rainfall was concentrated between December and May, and phenology of reproduction was strongly affected by the rainfall pattern. For each of the 11 most common species, discriminant analyses revealed the major abiotic characteristics that differed be- tween sites used and not used by those species. On a broader scale of analysis, Mantel tests showed no significant correlations among sites in the similarity of their abiotic character- istics and indices of similarity in their tadpole assemblages. There was also no concordance among sites between either type of similarity and actual proximity of locations. These results indicate that although individual species are responding to habitat characteristics and breed in sites having specific attributes, there are no large-scale species assemblages that covary in habitat use.

Global Biodiversity Conservation and the Alleviation of Poverty

Poverty and biodiversity loss are two of the worlds dire challenges. Claims of conservations contribution to poverty alleviation, however, remain controversial. Here, we assess the flows of ecosystem services provided to people by priority habitats for terrestrial conservation, considering the global distributions of biodiversity, physical factors, and socioeconomic context. We estimate the value of these habitats to the poor, both through direct benefits and through payments for ecosystem services to those stewarding natural habitats. The global potential for biodiversity conservation to support poor communities is high: The top 25% of conservation priority areas could provide 56%–57% of benefits. The aggregate benefits are valued at three times the estimated opportunity costs and exceed

Does the Spatial Scale of Experimentation Matter? A Test with Tadpoles and Dragonflies

1 per person per day for 331 million of the worlds poorest people. Although trade-offs remain, these results show win—win synergies between conservation and poverty alleviation, indicate that effective financial mechanisms can enhance these synergies, and suggest biodiversity conservation as a fundamental component of sustainable economic development.

GENETIC AND MORPHOLOGICAL VARIATION IN VANZOLINIUS DISCODACTYLUS : A TEST OF THE RIVER HYPOTHESIS OF SPECIATION

We report the results of a study designed to examine whether the spatial scale of experimentation in artificial ponds (cattle watering tanks) influences the results of manipulative studies of competitive and predatory interactions. The experiment consisted of two initial densities of Rana utricularia (Ranidae) tadpoles (0.035 and 0.14 animals/L) and the absence or presence (0.005 animals/L) of predatory Tramea lacerata (Odonata, Libellulidae) naiads in each of two water depths in cattle tanks of equal dimensions. Depth of tank did not significantly affect survival rate of tadpoles either as a main effect or as part of any interactive effect. At low tadpole densities the addition of predators decreased tadpole survival rates significantly, but at high tadpole densities they increased them sig- nificantly. Length of larval period increased significantly with increases in the density of surviving tadpoles at similar rates at both water depths, but deeper tanks produced sig- nificantly longer larval periods for the same tadpole density. Size at metamorphosis de- creased significantly with increases in the density of surviving tadpoles, but it decreased at a significantly faster rate in the shallower tanks. The results indicate that experiments at smaller spatial scales do not necessarily distort the numerical dynamics in this system but that they can overestimate the importance of density variation in producing variation in some phenotypic characters.

AQUATIC PREDATORS AND TADPOLE PREY IN CENTRAL AMAZONIA: FIELD DATA AND EXPERIMENTAL MANIPULATIONS'

Allozyme and morphological variation among populations of an Amazonian frog were analyzed to test for a riverine effect on population differentiation. High levels of genetic diversity within populations and genetic diversification among populations were found. Although correlations between genetic and geographic distances of population pairs were positive, they were not significant and indicated that sites that were close geographically were not genetically more similar. Only one of the 15 polymorphic loci showed any variation in allozyme frequency attributable to the presence of the river, but none of the overall among-population component of allozyme frequency variation (FST = 0.368) can be attributed to the river (FRT = 0.000). Significant differences in morphology (corrected for size differences) were found among the 11 populations in canonical variate space. In univariate Nested ANOVAs, five of the 12 morphological variables showed significant differences due to the presence of the river. However, cluster analysis performed on all morphological variables failed to detect obvious groups based on river bank locality. We could detect no congruence of pattern between morphological and genetic variation among populations. These results suggest that morphological characters may evolve at different rates than detectable allozyme differentiation.

The effects of reproductive phenology on larval performance traits in a three-species assemblage of central Amazonian tadpoles

Experimental manipulations of aquatic predators (odonate naiads and fishes) and prey (three tadpole species: Osteocephalus taurinus, Phyllomedusa tomopterna, and Epipedobatesfemoralis) investigated the role of predators in the organization of a tropical larval anuran assemblage. Eighteen months of surveys of 31 primary forest lentic sites examined phonological patterns of tadpole and predator species. I tested for a relation between predator and metamorph presence using the Mantel-Haenszel chi-square. I tested for differences in survival and development for each tadpole species as a function of predator identity. I examined correlations between growth of surviving tadpoles and both the number of nonspecific and the total number of surviving tadpoles. Two-way ANOVAs tested for differences in predation rate among predators and experiments. Finally, I tested for dif- ferences in selectivity for each prey species. Odonate naiads were the most common predator in upland isolated pools and peccary wallows, while fish were most common in lowland, stream-associated habitats. No relation was found between the presence of metamorphs and of predators in natural sites, except for metamorph presence (a positive relation for all tadpole species pooled) and presence of aeshnid larvae in natural sites. Predators reduced tadpole survival in three of four different prey-species combinations. Aeshnid naiads were the most effective predators, followed by libellulid naiads. Fish were never the most effective predators and their effect was variable. Predation rate on each of the three prey species varied among predators and sometimes depended upon which species were present, indicating that predation rate in the system was a function of the particular combination of prey species. No significant differences were found in selectivity for any prey species among individual predator types. All predators, however, preferred P. to- mopterna, the less abundant species, over 0. taurinus whenever the two species were together. Growth of tadpoles was inversely related to the number of surviving nonspecific tadpoles. Predators, therefore, have the potential to modify the composition of tadpole species assemblages through differential predation.

Predator-prey size interaction in tropical ponds

Two sets of experiments investigated how breeding phenology affects interactions among 3 tadpole species in Central Amazonia. Experiments were performed to test for effects of time of introduction of two later-breeding species (Phyllomedusa tomopterna or Epipedobates femoralis) on their own larval performance and on that of an earlier-breeding species (Osteocephalus taurinus)

PRELIMINARY CHECKLIST OF THE HERPETOFAUNA OF THE UPPER RIO URUCU, AMAZONAS, BRAZIL

An experiment was set-up to see in mortality inflicted by tadpole predators depends on prey and predator sizes. Fish and dragonfly larvae were used as predators and two size classes of Osteocephalus taurinus tadpoles as prey. Results show that the effect of predators is dependent on the size structure of the prey population. Furthermore, dragonfly larvae are more voracious predators than the fish used in the experiment. Both predators occur in natural ponds where Osteocephalus taurinus lays its eggs. The timing of arrival of predators and prey, which determines the relative sizes of predators and prey, is an important factor determining the outcome of an episode of community interaction in tropical ponds, as in similar temperate systems.

Natural history notes on frogs from Manaus, Amazonas

Thirty-three species of anuran amphibians and 22 species of reptiles were found in 9 days and nights of sampling in an unexplored region of Central Amazon. The community is characterized by typical lowland Amazonian species. The relatively short sampling time and high number of species caught indicates that this region probably has very high species richness.