Body size cascades from Neodiprion sawfly hosts to Perilampid parasitoids: An investigation of sequential divergence

Perilampus neodiprioni shows host-associated body size variation that mirrors size differences between its Neodiprion hosts, including Neodiprion lecontei and Neodiprion pinetum.

• Why it matters: Sequential divergence in parasitoids of externally feeding insects has not been identified, even though host ecological divergence could cascade into parallel specialization.
• What they did: Using by-catch samples, the study measured P. neodiprioni body size from Neodiprion lecontei and Neodiprion pinetum, modeling variation with host species, parasitoid sex, host sex, host cocoon size, latitude, and interactions. It also used mixed models for three size-based facial features and assessed abdominal-region size plus sexually dimorphic characters.
• The result: Host-related size variation in P. neodiprioni occurs in the abdominal region and in two sexually dimorphic characters, supporting possible reproductive isolation and suggesting a pathway for sequential divergence.

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