A new ant-butterfly symbiosis in the forest canopy fills an evolutionary gap

Myrmecophilous butterflies can establish complex symbiotic relationships with ants. A caterpillar wandering among the brood of the aggressive ponerine ant Neoponera villosa was found inside the core of a nest built in the myrmecophytic bromeliad Aechmea bracteata. This is the first caterpillar found living inside a ponerine ant nest. Its DNA barcode was sequenced, and an integrative approach was used to identify it as Pseudonymphidia agave, a poorly known member of the subtribe Pachythonina in the riodinid tribe Nymphidiini. The cuticle of the tank-like caterpillar lacks projections or tubercles and is covered dorsally by specialized flat setae that form an armor of small plates. Ant-organs potentially related to caterpillar-ant signaling, such as perforated cupola organs and tentacle nectary organs, are present. These morphological traits, together with evidence of social integration (direct contact with host brood, protective morphology, slow movement, no host aggressiveness), suggest that P. agave is a symbiotic, social parasite of N. villosa, preying on its host brood. However, several knowledge gaps remain, including oviposition site, dependence on bromeliad association, steps to colony integration, and larval diet through development. Carnivory has been reported in all known members of the subtribe Pachythonina (caterpillars prey on honeydew-producing hemipterans) suggesting a shift to myrmecophagy inside the ant nests as a possible evolutionary transition.

Filling the gap: a new ant-butterfly symbiosis in the forest canopy

Myrmecophilous butterflies can establish complex symbiotic relationships with ants. An elusive symbiotic caterpillar wandering among the brood of the aggressive ponerine ant, Neoponera villosa, was found inside the core of a nest built in the myrmecophytic bromeliad Aechmea bracteata. This is the first caterpillar found in symbiosis with a species of the subfamily Ponerinae. Tissue sample was barcoded, and an integrative approach was used to identify it as Pseudonymphidia agave, a poorly known Pachythonina member in the riodinid myrmecophilous tribe Nymphidiini. The caterpillar has a general tank-like body morphology, without projections or tubercles, and is covered dorsally by specialized flat setae that form an armor of small plates. Ant-organs potentially related to the caterpillar-ant signaling, such as perforated cupola organs and tentacle nectary organs, are present. These functional traits, together with the stable social integration, suggest that P. agave is a specialized social parasite of N. villosa. However, several knowledge gaps remain, notably the oviposition site, dependence on bromeliad association, steps to colony integration, and the larval diet through ontogeny. Carnivory has been reported in all known members of the Pachythonina subtribe (caterpillars prey on honeydew-producing hemipterans), and a shift to myrmecophagy inside the ant nests is a possible evolutionary step.

Modelling Extreme Rainfall Using Adjusted Sandwich Estimator

The Generalized Extreme Value (GEV) distribution is often used to describe the frequency of occurrence of extreme rainfall. Modelling the extreme event using the independent Generalized Extreme Value to spatial data fails to account the behaviour of dependency data. However, the wrong statistical assumption by this marginal approach can be adjusted using sandwich estimator. In this paper, we used the conventional method of the marginal fitting of generalized extreme value distribution to the extreme rainfall then corrected the standard error to account for inter-site dependence. We also applied the penalized maximum likelihood to improve the generalized parameter estimations. A case study of annual maximum rainfall from several stations at western Sabah is studied, and the results suggest that the variances were found to be greater than the standard error in the marginal estimation as the inter-site dependence being considered. Key words: Generalized Extreme Value theory, sandwich estimator, penalized maximum likelihood, annual maximum rainfall