Question

Grey langurs found in the southern Western Ghats (SWG) and grey langurs in Sri Lanka (SL) look very similar. Nilgiri langurs (found in SWG) and purple faced langurs (found in SL) also look similar. If allopatry played a role in the early diversification of this group (at point X in the tree), which one of the phylogenetic trees is most likely to be correct?
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• A. P
• B. Q
• C. R
• D. S

Hint:

Phylogenetic analysis often hinges on understanding the geographic and ecological contexts that contribute to species diversification. In cases of allopatric speciation, look for tree structures that reflect clear separations likely caused by geographical barriers.

Answer 1

The Correct Option is C

Step 1: Analyze the structure of Tree R. Tree R begins with a split indicating a significant geographical or ecological separation between the grey langurs of SL and SWG. The lineage then further diversifies in SL to include purple-faced langurs, while maintaining grey langurs in SWG. This suggests that allopatric speciation influenced by geographical isolation led to the diversification within these regions. Step 2: Justify the selection of Tree R. The configuration of Tree R accurately represents how physical barriers and ecological factors could drive early diversification, resulting in distinct yet genetically related groups within the grey and purple-faced langurs. It effectively captures the essence of allopatric speciation and the evolutionary history as suggested by the similarities and distribution of the langur populations.