Morphology Of Fossil Salamanders Reflects Climate Change

Researchers analysed a late-Holocene fossil record to trackmorphological traits in the Tiger Salamander through the last 3,000years. The team, led by Elizabeth Hadly from Stanford University,United States, analysed trends in the fossil record within the contextof known climate change, to distinguish patterns of responsecorrelating to specific climatic periods during this time.

The fossils were all collected from Lamar Cave in YellowstoneNational Park in Wyoming, United States. The cave deposits were datedand divided into five time periods according to their estimated age.The researchers then grouped the fossils into four morphologicallydistinct groups: young larval, paedomorphic, young terrestrial or oldterrestrial, and measured the body size index (BSI) of fossils in eachgroup and time period.

The team found that paedomorphic individuals - sexually mature,yet still aquatic and retaining larval characteristics - were muchsmaller than terrestrial adult individuals, during the Medieval WarmPeriod (MWP). The authors claim that this is eveidence for a responseto warm and dry climate conditions, which allowed a terrestrialectotherm to flourish. They conclude that the fossil record of theTiger Salamander reflects known climatic conditions during the MWP, atime period characterised by a warm and dry climate that occurredapproximately 1150 to 650 years ago.

Based on these findings, the authors speculate that the futurewarmer and drier climate predicted for the Yellowstone region is likelyto create less permanent aquatic environments and select againstaquatic paedomorphic individuals. This scenario would decrease thevertebrate biomass and alter the food web structure in the aquaticsystem.

Article:
Temporal response of the Tiger Salamander (Ambystoma tigrinum) to 3,000 years of climatic variation
Judsen E Bruzgul, Webb Long and Elizabeth A Hadly
BMC Ecology 2005, 5:7 (13 September 2005)