Hi, my name is Diogo and what I’m going to present you is part of my master thesis that was submited to Biotropica about 3 months ago, I’m still waiting for the editor’s decision, which I hope to be positive.
Frogs choose their breeding sites according to landscape features and some biotic (presence of conspecifics, predators, and parasites). One of the most important landscape features influencing large-scale amphibian distribution is pond canopy cover
Additionally, previous works have found that Water chemistry variables are poor predictors of amphibian distribution at the landscape level. However, the influence of water chemistry and landscape features have never been tested together.
But both water chemistry and landscape features may vay in space. Thus spatial processes must be included in analysis if we want to have a wide understanding of species distribution. However, much of it has been based on theoretical work and few studies have addressed the effect of fine-scale spatial processes and environmental variables in organisms with strong dispersal limitation.
Additionally, juveniles usually breed on the same sites where they emerged, a behavior called philopatry. This behavioral mechanism can strongly influence spatial dynamics of amphibian metacommunities. However, their role in dictating large scale distributional pattern of amphibians has been only recently explored.
Here we studied for the first time the joint influence of water chemistry variables, pond morphology and canopy cover on the structure of a tropical tadpole metacommunity
We sampled tadpoles in 13 ponds in the Serra da Bocaina National Park, SE Brazil
Ponds varied greatly in canopy cover gradient
And their spatial arrangement
We measured five variables related to water chemistry and another set of variables related to pond morphology, in addition to pond canopy cover. We also generated spatial variables using a technique called PCNM, that created 5 variables
We analyzed these variables through a partial RDA, that separated the sole and shared influence of pond morphology, water chemistry, and spatial variables. As we sampled tadpoles throughout one year, to assign significance of each component the permutations were done within ponds.
And this is what we got. Water chemistry indeed didn’t explained a significant portion of tadpole abundance. Conversely, Pond morphology explained 16% and spatial variables 19% of tadpole abundance.
The two most important environmental variables were Pond canopy cover and floating vegetation
So, adult habitat selection is a possible mechanism creating spatial dynamics in this metacommunity, which largely affected tadpole abundance even at a fine spatial scale (~ 11 Km2) along with environmental variables, specially pond canopy cover and floating vegetation.
In conclusion, habitat connection and dispersal may have more profound effects than previously thought (e.g., Becker et al. 2007). Consequently, Habitat fragmentation can turn dispersal less adaptive to forest species, favoring high population isolation, reduced gene flow, and inbreeding.
1. Diogo B. Provete*Thiago Gonçalves-Souza Michel V. Garey Denise C. Rossa-Feres Itamar A. Martins
2. Regional Pool Open-canopy ponds Closed-canopy ponds
3. Introduction________________________ The role of water chemistry vs. landscape attributes on large scale distribution of anurans
5. Aim____________________________ Test the joint influence of water chemistry, pond morphology, and spatial variables on tadpole abundance at a fine spatial scale (11 Km2)
6. August 2008 to January 2009
7. PP4 PP3 AP1 AP2 PT1 PT3 PT2 PP1 PP2
8. Material & Methods__________________ Environmental variables Water chemistry (pH, DO, Temp, Conduct, and turbidity) Pond morphology (area, depth, and floating vegetation) % Pond canopy cover Spatial variables Spatial EigenVector Modelling a.k.a PCNM (forward selection; Blanchet et al. 2008) => 5 PCNM
9. Material & Methods__________________ Data analyses Variation partitioning => partial RDA => shared and sole influence of water chemistry, pond morphology, and space on tadpole abundance Permutation stratified within ponds, month as a factor
11. EnvironmentalHabitat selection by gradients (canopy, adults (philopatry) vegetation) t al 16% o n m en ir ed en v ru ctur ients tial ly st grad S pa Fine-scale Spatial Dynamics (pond network) 20% Tadpole Abundance
12. Conclusion______________________ Dispersal limitation and fragmentation Perspectives Incorporate broad vs. fine scale spatial processes How philopatric behavior (niche-based process) and neutral dynamics create spatial patterns => simulations
13. Thank you! email@example.comWeb site => http://bit.ly/frogs_atbc Student Travel Award