Full text
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| Author(s): |
Marilia Palumbo Gaiarsa
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-09-10 |
| Examining board members: |
Marcio Roberto Costa Martins;
Cristiano de Campos Nogueira;
Ricardo Jannini Sawaya
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| Advisor: | Marcio Roberto Costa Martins |
| Abstract | |
Given the present biodiversity crisis and the lack of available resources, threatened species must be differentiated from each other so that those at higher risk can be attended first. Within lineages, species differ in their need for conservation action and in their relative importance for conserving current and ancient ecological and evolutionary diversity. We here propose a new approach to create a priority index (PI) for species within monophyletic groups, by combining life history traits, ecological singularity, and phylogenetic distinctness. Our model lineage was the tribe Pseudoboini, a group of Neotropical snakes for which we gathered literature data, unpublished observations provided by other researchers, as well as original data from museums specimens. To create the PI, we combined three different indices: vulnerability to extinction (IVE), ecological oddity (EO) and phylogenetic distinctness (PD). IVE was calculated by ranking species according to a combination of six factors known to affect snake population survival (body size, mean fecundity, dietary breadth, geographic distribution, altitudinal range, and ability to persist in altered habitats). Ecological oddity, which takes into account the distance of a given trait of a given species in relation to the lineage mean for that trait, was calculated for four characters (body size, mean fecundity, habitat breadth, and dietary breadth), and PD takes into account how relictual a given species is. There was a great amount of variation in the biological variables among pseudoboines. IVE was evenly distributed across the Tribe. Oxyrhopus petola presented the lowest IVE and Clelia langeri the highest. Besides the latter, five additional species showed high IVEs: Pseudoboa serrana, Clelia scytalina, Clelia hussami, Siphlophis compressus, and Pseudoboa martinsi. Phimophis iglesiasi, which seems to be the sister species of all pseudoboines, showed the highest PD. Except for Clelia errabunda, Oxyrhopus doliatus, and Phimophis chui, most species presented low EO values. The lowest PI was obtained for Oxyrhopus melanogenys and the highest for Phimophis iglesiasi. Besides the latter, Clelia hussami, P. chui, C. langeri, and C. scytalina also presented high PIs. Only two species with high IVE in our study are included in red lists (Clelia langeri and Siphlophis longicaudatus), and five additional species appeared with high IVEs; thus, all these species should receive special attention in future assessments of extinction risk. Species with higher vulnerability to extinction were also those with higher phylogenetic distinctness, reinforcing the importance of conserving relictual species. Representatives from almost all clades within the pseudoboines are listed amongst the ten higher PI values, what maximizes the phylogenetic diversity of the prioritized taxa. Although it is not possible to compare values obtained in studies with different lineages (the indices generated are cladespecific), when extended to more inclusive lineages within a group of organisms (e.g., subfamilies, families) this approach might enhance the quality of future prioritization processes. (AU) | |