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Southeast Ecological Science Center


DEVELOPMENT OF GENETIC TOOLS TO BETTER UNDERSTAND MANATEE POPULATION BIOLOGY

Robert K. Bonde1 and Peter M. McGuire2

1 U.S. Geological Survey, Florida Integrated Science Center;
2 Department of Biochemistry & Molecular Biology, University of Florida

Presented at the Manatee Population Ecology and Management Workshop,
1-4 April 2002, University of Florida, Gainesville, Florida.
 

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ABSTRACT

Long-term field observations, with the aid of photo identification and radio-tracking technology, have necessitated the re-evaluation of data on life history parameters gathered from the field. Early studies revolving around manatee genetics have included analyses of allozymes, cytochrome-b, and the d-loop of the mitochondrial control region.  However, recent advances in molecular genetic analysis techniques will allow field biologists to ask specific questions to help clarify and define observed relationships between kinship-groups (paternity and maternity) using microsatellites.  In addition, important information on manatee behavior, potential reproductive strategies and success, analysis of population genetic structure based on both nuclear and mitochondrial DNA markers, and assessment of critical habitat, such as feeding and wintering grounds, will be amassed to help clarify population parameters.  Specifically, the use of microsatellite "fingerprinting" holds great potential for better understanding manatee population biology and genetic structure. This information will be necessary in evaluating current and future management and research strategies.

Future research is directed towards both cytogenetics and molecular sequencing.  Chromosome banding studies are planned for utilizing probes for allele marking and identification to recognize specific genes related to disease processes.  Studies of mitochondrial DNA haplotype sequencing recently have been completed by researchers at the USGS Sirenia Project and the University of Florida and show distinct populations of West Indian manatees throughout their range.  Additional sample analyses from international cooperators are encouraging and continuing.  Currently, progress is being made to isolate specific primers (probes) to be used for manatee DNA fingerprinting studies.  For the past several years the USGS and FMRI have amassed a collection of samples obtained from both wild and dead manatees in the field and archived for anticipated future analysis.  Currently, geneticists are ready to begin examining these samples.  In Florida this is a collaborative effort between the USGS, FMRI, UF, Mote Marine Lab, and Wildlife Trust.

mtDNA Haplotypes throughout the manatee range - click to enlarge
Manatee - (Trichechus manatus latirostris) - click to enlarge

mtDNA Haplotypes throughout the manatee range

PRIMARY OBJECTIVES

  • Continue development of specific manatee genetic probes to identify polymorphic microsatellite loci.
  • Evaluate these genetic markers for use in mark-recapture analysis, life history assessment, stock fitness, and investigating reproductive biology including paternity and inbreeding.
  • Design interagency protocols for archiving, analyzing, and evaluating manatee genetic tissues.
  • Refine the techniques and approaches for obtaining genetic samples from wild, free-ranging manatees.
  • Test zoo-FISH probe markers for cytogenetic applications and subsequent evaluation.  Coupled with immunology, this could be a very useful tool in understanding manatee evolution and disease processes.

MANATEE MICROSATELLITE PRIMERS

Characteristics of 15 microsatellite markers - click to enlarge
Electropherogram - microsatellite - click to enlarge
Molecule - click to enlarge
Manatee karyotype - click to enlarge

Manatee karyotype

DISCUSSION

Increasing habitat loss and high mortality are factors which threaten the future of the Florida manatee. Low intrinsic reproductive rate and low natural population density make this species particularly vulnerable to human perturbations. One consequence of population reduction is loss of genetic diversity.  Several generations of severe inbreeding in a small population or repeated crashes to a few individuals can deplete most of the genetic variation from an initially larger population (Soulé 1987).  It is generally recognized that genetic variability is necessary for both adaptation to changing environments and long-term survival of the species (Ralls et al. 1979). Strategies to preserve genetic diversity require knowledge of the distribution of variation within populations and among species.

Results in terms of disease susceptibility and genetic lineage will be available and aid managers in assessing future recovery efforts. This information will help shed light on the frequency of different lineages or family units present in each geographic area, as well as the level of genetic flow between those areas.

Definition of the Florida manatee population structure and reproductive behavior will have conservation implications.  Some management decisions may benefit from the recognition of family relationships within geographic or wintering groups as expressed by management units. For example, should depleted manatee populations be supplemented by translocation from other areas? Should a rehabilitated manatee be released in any appropriate location indiscriminately? Misdirected transplantation or translocation could compromise the integrity of genetic differences which have accumulated over evolutionary time. The definition of family units will help to avoid inbreeding events if animals need to be placed in semi-captivity for long periods of time before they are returned into the wild.

ACKNOWLEDGMENTS

This work is a product of a very large cooperative effort between the U.S. Geological Survey, the U.S. Fish and Wildlife Service, the Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, and the University of Florida. Much of the foundation for our understanding of Florida manatee genetics is based on doctoral work completed in 2000 by Angela Garcia at the University of Florida.

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