Time progression of specification

Biology

Species within a given population will differentiate due to a sudden and dramatic geological or climatological change. If a volcano erupted on an island like one of those on Vanuatu, the populations of local geckos would start to differentiate depending on where members of that population were before and after the eruption.

Statement/Hypothesis: If a volcanic eruption led to lava flows on one side of the island, but not on the other side, then the gecko population would differentiate based on the availability of food sources and also based on the remaining predators.

Geological Event: A volcano erupts on a small tropical island, part of the Vanuatu group. The types of observations necessary for the evaluation of the impact of the volcano on local lizard (gecko) species include size (length), coloration and visual patterns, and vocalizations. Behavioral observations would include territories occupied, feeding patterns, and mating patterns.

Characteristics of the Two Environments: Before the volcano erupted, the island of only 300 square miles in area revealed little in the way of regional diversity. The island had a volcanic soil and some rich mineral veins. Foliage was dense throughout, but with some plant diversity depending on elevation. Moreover, the windward and leeward sides of the island differed in their vegetation and prevalence of certain gecko species. After the eruption of the volcano, the windward and leeward sides of the island shifted dramatically. The leeward side received the majority of the heavy lava flows and was henceforth characterized by treeless terrain over great swathes of land; whereas the windward side remained relatively unchanged.

Changes to the Two Populations: Geckos that were prevalent on the leeward side of the island started to grow larger, as their primary predators were impacted adversely by the lava flows. As species of endemic tree snake lost much of its habitat on the leeward side of the island, resulting in greater survival of young geckos and a longer life span. As a result, the geckos on the leeward side of the island also ceased to engage their defenses as readily, and became bolder as well as bigger. The coloration of the leeward geckos became brighter, as they no longer needed to camouflage to deter predators. Cats, introduced to the island by humans, also preferred the thicker foliage for hunting that remained on the windward side of the island. On the windward side, the numbers of predators vs. geckos remained roughly the same after the eruption of the volcano. Biodiversity ironically increased as a result of the eruption, which helped to wipe out the invasive species of mongoose that had been introduced several decades earlier. However, the mongooses are expected to increase in number once again due to their rapid rates of reproduction and generally hearty nature. The increase in gecko diversity on the leeward side is predicted to be temporary. Food sources for the gecko, especially insects, would also result in dramatic size changes for the leeward vs. windward populations. With a large portion of the vegetation vanishing from the leeward side, the geckos there would be eating different types of insects and likely smaller ones.