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DNA and the Origin of North American Pumas by Dr. Melanie Culver The University of Arizona, School of Natural Resources The puma is one of the most geographically diverse species living today. It occupies the largest latitudinal range of any new world terrestrial mammal (110 degrees in latitude), as well as a large altitudinal range (from sea level to 14,800 feet above sea level). In the early 1900s, the puma (Puma concolor) was described with high subspecies diversity, with 32 distinctly named subspecies that were fairly evenly distributed throughout their broad geographical range. These subspecies descriptions were based on several morphological features (coat color, pelage, skull, and skeletal measurements); however, not all specimens compared were full adults, and many of the subspecies were described based on one or a few individuals. Molecular genetic tools provide an alternate method to describe subdivisions within a species and to examine the accuracy of 32 subdivisions for pumas. Morphological methods provide an important tool for taxonomy as do molecular genetic methods. Yet if the incorrect marker or trait is selected, both methods can lead to anomalous results. The advantage of using molecular markers over morphometrics is that they allow the selection of markers that are neutral (having no effect on physical character- Wild Cat News istics and thus not under selection) and independent (not on the same chromosome). Neutral markers are important because they give an indication of the amount of time that non-interbreeding populations have been separated; independent markers are important because they allow acquisition of several separate lines of evidence towards a conclusion, and if most of the markers provide the same result, it can be assumed that the conclusion is not guided by a single anomalous marker. Molecular genetic markers can be used to resolve subspecies divisions, relying on the assumption that genetic changes accumulate in a predictable manner over time. If populations do not interbreed, given enough time, these changes can be used to distinguish among those populations. Two classes of molecular genetic markers were used to examine subspecies-level subdivision in pumas: DNA sequence variation for mitochondrial genes, which occur outside the nucleus of the cell, and DNA fragment length variation for 10 nuclear microsatellite loci. Mitochondrial sequence variation is widely used as a genetic marker to resolve species or subspecies-level taxonomy, population subdivision, gene flow, and maternal lineage assessment. Highly polymorphic nuclear microsatellite markers are useful to estimate relatedness among individuals, population subdivision, gene flow, subspecies-level taxonomy, and can distinguish among all individuals of a species. When combined, these markers provided 11 independent lines (Continued on Next Page) www.cougarnet.org DNA and the Origin of North American Pumas (Continued from Previous Page) of evidence to examine subspecies designations in pumas. When more than 300 pumas were analyzed, throughout North and South America, all 11 markers were in agreement. These molecular data indicated that South American pumas contain high levels of genetic diversity for both mitochondrial and microsatellite DNA. In contrast, pumas throughout Central and North America (north of Nicaragua) had almost no mitochondrial DNA variation and only moderate levels of microsatellite DNA variation. This pattern of variation formed the basis for establishing one puma subdivision north of Nicaragua. The level of genetic variation observed in South America resulted in recognizing five puma subdivisions south of Nicaragua. Furthermore, the presumed boundaries for these six groups of pumas incorporated major geographical features. Extending from north to south within the geographical range of pumas, the first boundary occurs in Nicaragua (potentially in the “lake region”), and the other boundaries incorporate several major rivers in South America (Amazon River, Rio Parana, Rio Negro, Paraguay River). Molecular markers that are neutral can estimate time elapsed since populations became isolated. In estimating timing for the subdivision of puma populations, two themes emerge; North America is the most recently founded population and the population inhabiting the Brazilian Highlands is the oldest. Additionally, molecular evidence indicates that pumas, as a species, are only 390,000 years old. Another method to estimate the timing for species existence is the fossil record. In the case of pumas, the oldest fossils are approximately 300,000 years old, remarkably similar to the molecular date; however the fossil record does not indicate that North American pumas are a more recent lineage (puma fossils on both continents are equally old). The disagreement of the North American fossil record (which indicates equal age for North and South American pumas) with the molecular data (which indicates North American to be more recent than South American pumas), leads to the conclusion that pumas were extirpated in North America more recently than 300,000 years ago. If this is true then pumas in North America today are the result of a relatively recent re-colonization event. The most likely timing of the extirpation would be 9,000 to 12,000 years ago to coincide with the Pleistocene extinctions. Therefore, the North American puma lineage may be only a few thousand years old. This presumed young age for North American pumas is directly related to the lack of genetic diversity and differentiation observed in current North American pumas. Given the potentially young age of North American pumas, it is no surprise that genetic analyses indicated only one subspecies in North America. In summary, several conclusions can be made regarding subdivision and population genetics in pumas. 1) Pumas originated in the Brazilian Highlands approximately 300,000 years ago. 2) A possible extirpation and re-colonization has occurred in North America. The potential timing of this re-colonization event is subsequent to the most recent ice age which ended approximately 10,000 years ago. 3) Molecular data does not support 32 subdivisions for pumas; instead six subspecies-level groups are indicated. 4) Within these six groups pumas are fairly panmictic. These conclusions are relevant to current conservation efforts in pumas. Since pumas appeared to be fairly panmictic within the six broadly defined groups, fragmentation of habitat will drastically change the observed, historically determined, patterns of subdivision. Managers should strive to maintain historical habitat connectivity within the six large groups defined by this data set. Additionally, managers should take into account the revised subspecies designations suggested by this data set, with respect to restoration of populations that are declining or endangered. © Daniel J. Cox/NaturalExposures.com Wild Cat News www.cougarnet.org