Kaitlyn M. Dalrymple
Mestrado | 1° ano
Consequences of host-range expansion under the Stockholm Paradigm - empirical evaluation of monogenoid population dynamics between sympatric hosts
Consequences of host-range expansion under the Stockholm Paradigm - empirical evaluation of monogenoid population dynamics between sympatric hosts
The Stockholm Paradigm encompasses core ecological hypotheses (ecological fitting, oscillation hypothesis, and taxon pulse) to characterize the effect of fluctuations between exploration and exploitation of a sloppy fitness space by organisms, often due to environmental perturbations, as the potential for production of new phylogenetic lineages and sequential speciation events. For parasites, this is demonstrated when a parasite colonizes a new host species - also referred to as host-range or host-repertoire expansion. Based on both empirical and modeling data, these colonist populations frequently present the founder's effect which reduces genetic diversity much like a genetic bottleneck. Our objective is to examine sequences from monogenoid parasites found in sympatric hosts in two separate case studies: the first consists of two species of Platyhelminthes Monogenoidea (Hexabothridae and Loimoidae) collected from cryptic, sympatric Sphyrna spp. (Chondrichthyes) from South Carolina, USA. The second consists of sequences from three species of Gyrodactylidae from sympatric Corydoras spp. (Siluriformes) from Paraná, Brasil. These different host-parasite models will be analyzed using Approximate Bayesian Computation (ABC). We hypothesize lineages demonstrating founder’s effect represent the distinction between the original and novel hosts; alternatively, absence of a genetic bottleneck could be attributed to sustained gene flow between populations. The complexity of the life cycle could be one determining factor for sustained gene flow, thus we can compare models for the oviparous monogenoids (transmitted as larvae) of the Sphyrna hosts with the viviparous monogenoids (continuous transmission) of the Corydoras hosts. As climate change alters the ranges of megafauna, we may observe the greater potential for host-range expansion in pathogens and parasites.