Friday, April 03, 2015

Detecting African Manatee Populations

A new genetics study just completed as part of my dissertation research has defined African manatee populations across their large range (21 countries) for the first time. Over eight years I collected 78 manatee tissue samples from eight countries and successfully isolated DNA from 63 of them in order to determine where distinct populations of the species occur. Collecting the samples was actually the hardest part of the study, because manatees in Africa live in very remote places, and even when samples were collected (from carcasses, live manatees rescued or captured for studies, and from manatee bushmeat in markets) it sometimes took over a year to get the proper export permits to send them to my lab in the USA for analysis. Most of the samples came from Senegal and Gabon, because those are the studies where I have long-term study sites. Other samples were collected during trips to other countries or provided by collaborators working in those countries. I studied two mitochondrial genes which are commonly used for population genetics because they can inform us about deeper evolutionary levels, and populations rather than individuals. I identified different haplotypes, which are a unique combination of forms of a gene found on same chromosome. That sounds complicated, but think of haplotypes being ice cream, and the different combinations are like different flavors. For example, mocha chip and mint chocolate chip are more similar to each other than to strawberry ice cream because they both have chocolate chips. In the same way, some haplotypes are mostly closely related to each other and are from the same population, whereas others are more distantly related and are from different populations.

My research identified 25 new haplotypes for the African manatee, which is exciting since only five had been identified prior to this study. The study identified four populations: one in West Africa (coastal Senegal, Guinea, and Guinea-Bissau), a separate population in the Senegal River, an inland Niger River population that included samples from Mali, Niger, Chad and Cameroon, and a large population in West and Central Africa (Ivory Coast, Ghana, Benin, Cameroon, and Gabon). This study is a first step and once it is published, we will continue collecting and analyzing samples in order to continuing defining more fine-scale population structure.  

Here's a map of DNA (control region) haplotypes identified in 63 African manatee samples. Sixteen new (solid colors) and five previously published haplotypes (patterns; Vianna et al. 2006) are shown in pie charts. Circle size corresponds to the total number of samples per country, and slices are proportional to haplotypes found (see inset table). Asterisks (*) indicate previously published haplotypes identified by this study at four new locations.

By defining manatee populations across Africa, this work aids conservation efforts for the species by informing wildlife managers in many countries about where unique populations exist, where they can focus trans-boundary conservation and management efforts (when populations occur across borders), and where efforts need to be targeted to specific locations where manatee populations are isolated. My co-authors and I are very excited to publish this work in the scientific literature soon!

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