New Data Indicate Larger Decline in Morphological Diversity in Split-Footed Lacewing Larvae than Previously Estimated

Area of Science:

• Paleontology
• Entomology
• Evolutionary Biology

Background:

• Insect declines are a growing concern, prompting research into historical patterns.
• Neuroptera (lacewings) have been hypothesized to have declined post-Cretaceous, with larval morphology studies supporting this.
• The split-footed lacewing family, Nymphidae, is a notable group within Neuroptera experiencing significant decline.

Purpose of the Study:

• To investigate the extent of decline in Nymphidae using newly discovered fossil larvae.
• To assess the impact of increased specimen numbers and morphological data on recognizing historical insect decline.
• To identify specific morphological regions that best signal diversity loss.

Main Methods:

• Analysis of 13 new larval specimens of Nymphidae from 100-million-year-old Kachin amber, Myanmar.
• Expansion of the dataset to 60 specimens for morphospace analysis.
• Detailed examination of larval head, mouthparts, and trunk morphology.

Main Results:

• The expanded dataset revealed increased morphospace, indicating that the Nymphidae family diversity was likely underestimated.
• A significant loss of diversity was most strongly indicated by the morphology of the head and mouthparts, linked to feeding ecology.
• Analysis of the trunk region did not recover a clear signal of diversity loss, potentially due to preservation biases and early developmental stages of fossil larvae.

Conclusions:

• The decline in Nymphidae is likely more substantial than previously recognized.
• Head and mouthpart morphology are critical indicators of past insect diversity loss.
• Fossil preservation constraints can influence the interpretation of morphological diversity and decline signals.