The Christie Lab

Purdue University


Evolutionary rescue in a host-pathogen system results in coexistence not clearance

The evolutionary rescue of host populations may prevent extinction from novel pathogens. However, the conditions that facilitate rapid evolution of hosts, in particular the population variation in host susceptibility, and the effects of host evolution in response to pathogens on population outcomes remain largely unknown. We constructed an individual-based model to determine the relationships between genetic variation in host susceptibility and population persistence in an amphibian-fungal pathogen (Batrachochytrium dendrobatidis) system. We found that host populations can rapidly evolve reduced susceptibility to a novel pathogen and that this rapid evolution led to a 71-fold increase in the likelihood of host–pathogen coexistence. However, the increased rates of coexistence came at a cost to host populations; fewer populations cleared infection, population sizes were depressed, and neutral genetic diversity was lost. Larger adult host population sizes and greater adaptive genetic variation prior to the onset of pathogen introduction led to substantially reduced rates of extinction, suggesting that populations with these characteristics should be prioritized for conservation when species are threatened by novel infectious diseases.

Evolutionary rescue in a host-pathogen system results in coexistence not clearance. Evolutionary Applications. Link to paper (open access).


Doctoral position available: 

Graduate position in Population Connectivity of Great Lakes Fishes 

A PhD position is available in lab of Mark Christie at Purdue University for a highly-motivated candidate interested in local adaptation, larval dispersal, conservation and population genetics in general. Similar to most marine systems, many Great Lakes fishes have a miniscule, but highly dispersive, pelagic larval stage that makes it challenging to directly determine patterns of population connectivity. However, such knowledge is critical for effective conservation and management efforts (e.g., MPA design). One way to assess patterns of population connectivity is with genetic methods.

For this position, the candidate should be interested working on a project examining patterns of population connectivity and larval dispersal in Great Lakes fishes. Previous research experience with molecular techniques, computational work, statistics, bioinformatics, and assisting with the design and implementation of experiments will be highly regarded. The student will also be expected to interact regularly with Tomas Höök and information about our labs and the graduate school can be found here:

If you are interested in joining the lab, please contact Mark Christie ( as soon as possible with a resume/CV and a brief description of your research interests and experience. Formal applications will be due to Purdue University by January 15th, 2018.


Disentangling the relative merits and disadvantages of parentage analysis and assignment tests for inferring population connectivity

New paper that systematically examines when and under what conditions parentage analysis outperforms assignment tests (and vice versa) for inferring populations connectivity.

Click on the link to see the full article here.