Date of Award

Summer 8-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

Dr. Brian Kreiser

Committee Chair Department

Biological Sciences

Committee Member 2

Dr. Carl Qualls

Committee Member 2 Department

Biological Sciences

Abstract

Liasis mackloti is currently recognized as three subspecies (L. m. savuensis, L. m. dunni and L. m. mackloti) inhabiting several islands o f the Outer and Inner Banda Arc of islands o f Indonesia’s Lesser Sundas Archipelago. We used partial mitochondrial cytochrome b sequences and morphological character states to examine and resolve the phylogenetic relationship o f these three subspecies. Maximum likelihood and parsimony analysis showed that Liasis fuscus is the sister lineage to the L. mackloti ssp. complex. There is strong support for the recognition o f three clades that are delineated by savuensis, dunni and mackloti. The current subspecies taxonomic scheme accurately delineates the evolutionary distinctiveness o f the various insular populations based on congruent topologies revealed by both the molecular and morphological data sets. The lineage is monophyletic, and each o f the three subspecies differs from the other two both morphologically and genetically. Given the morphological and genetic distinctiveness o f each taxon, we believe there is substantial empirical evidence and justification for the elevation o f the three species to full species status. Morphologically, there are several characteristics that differentiate the three subspecies including the location of the heat sensing pit on the labial scales (L. m. mackloti has heat sensing pits on labial scales 9, 10, 11 and 12, L. m. savuensis on labial scales 10, 11, 12 and 13, and L. m. dunni on 9, 10, 11, 12, and 13), number o f loreal scales (L. m. savuensis andZ. m. dunni have 1 while L. m. mackloti have 2), midbody scale row count (Z. m. savuensis has 46-49, Z. m. dunni has 52-63, and Z. m. mackloti has 59-65), and number of postanal scales (Z. m. savuensis has 65-76, Z. m. dunni has 85-89 and Z. m. mackloti has 88-93). In terms o f cytochrome b mitochondrial DNA sequence data, there is the greatest sequence divergence between Z. m. savuensis andZ. m. mackloti (5.6%), followed by Z. m. savuensis andZ. m. dunni (5.2%) and Z. m. mackloti and Z. m. dunni (2.6%). There was no sequence divergence between the three insular poulations studied o f Z. m. mackloti. Both molecular and morphological data sets reveal similar patterns o f phylogeny. Their distribution and evolution appears to have been shaped by combined effects o f dispersal and vicariance. We conducted pheromone trailing experiments to investigate the level of geographic variation present in this behavior in the macklot’s python, Liasis mackloti (Serpentes: Boidae). Three subspecies (Z. m. mackloti, L. m. savuensis, and Z. m. dunni) are currently recognized and are found on several o f the Lesser Sundas islands o f Indonesia including Sawu, Wetar, Timor, Semau and Roti. Based on prior studies, three clades have been delineated (Wetar, Sawu, and a Timor-Semau-Roti clade). The three subspecies display remarkable interpopulational (morphological, genetic and behavioral) variation but only slight intrapopulational polymorphisms. A modified Y-maze was used to test homotypic and heterotypic and male and female preferences both within and between insular populations. The results o f this study o f the Z. mackloti complex indicate that during the breeding season male pythons were able to discriminate between homotypic and heterotypic odors within each of the clades (P<0.05). However, male pythons from Timor, Semau and Roti were unable to differentiate pheromone trails produced by females from these three islands (P>0.05). Male L. m. dunni from the island o f Wetar are generally longer than females and also exhibited specificity toward homotypic male trails. This homotypic male trailing behavior, in addition to several male-male combat interactions observed during the study suggests that males from Wetar may attempt to displace males for access to females. Pheromone trailing discrimination is an important pre-zygotic reproductive isolating mechanism that may have played an important role during speciation. We also present the role of dispersal and vicariance in shaping current patterns o f geographic variation. Courtship behaviors were compared between three subspecies of the Indonesian water python, L. m. mackloti, L. m. savuensis, and L. m. dunni, to elucidate patterns of geographic variation in male courtship behavior in standard laboratory conditions. The three subspecies are found on a series o f island that are part o f the Outer Banda Arc and Inner Banda Arc of the Lesser Sundas Archapelago. The insular populations o f L. mackloti ssp. within this archipelago indicate that separation between islands during the Pleistocene played a role in determining current assemblages and variation within species. The islands o f eastern Indonesia form biogeographic subregions that have relatively high levels o f endemism and evidence o f incipient speciation as a consequence o f changes in sea-levels and climate during the Pleistocene. Two predominant models to explain the biogeography o f L. mackloti ssp. include vicariance and dispersion, both of which likely played an important role in shaping the distribution pattern o f these pythons that we currently observe and are discussed in this chapter. L. mackloti generally adheres to the triphasic schema including tactile-chase, tactile-alignment, and intromission and coitus. However, the use o f the pelvic spurs during tactile-chase and tactile-alignment is a unique boid-typical motor pattern and likely plays an important premating reproductive isolating mechanism that prevents interbreeding between conspecific individuals. Behavioral sequence chains were derived from videotaped experimental tests and subjected to transition analysis. We observed variation in both the frequency of occurrence and the sequence o f the principal courtship behaviors and, when compared statistically, most o f these behaviors differed between populations. We observed geographically unique island patterns in the sequence in which male courtship behaviors are displayed. Our data yielded the following information: 1) the courtship sequence in all three subspecies is not random; 2) the sequence o f L. m. savuensis is much less complex than that o f L. m. mackloti and L. m. dunni', and 3) the tactile pelvic spurring target sites used by males on the females’ dorsum is different between the three subspecies. We also determined whether sexual isolation among selected populations existed. In the first study, we performed male-female reciprocal crosses o f pythons between two different insular populations and measured mating success and whether eggs were produced. The results o f this test reveal that sexual isolation occurs between the three defined subspecies. The behavioral differences in regards to courtship sufficiently delineate the subspecies and no significant difference was detected when comparing the three different island populations o f L. m. mackloti (Timor, Semau and Roti), however, they were significantly different than L. m. savuensis and L. m. dunni. The historical isolation o f Sawu and Wetar Islands, and connection o f Timor, Semau and Roti Islands reveals interesting biogeographic patterns and the snake fauna o f islands within the Lesser Sunda group indicate that separation between islands during the Pleistocene played a role in determining current assemblages and variation within species detected in this study.

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