6. Aim____________________________
Test the joint influence of water chemistry,
pond morphology, and spatial variables on
tadpole abundance at a fine spatial scale
(11 Km2)
10. 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
11. 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
14. Environmental
Habitat 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
15. 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
16. Thank you!
dbprovete@gmail.com
Web site => http://bit.ly/frogs_atbc
Student Travel Award
Editor's Notes
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.