Effectiveness of the aposematic Eumaeus childrenae caterpillars against invertebrate predators under field conditions

Abstract

Effectiveness of the aposematic Eumaeus childrenae caterpillars against invertebrate predators under field conditions. Eumaeus childrenae (Lepidoptera, Lycaenidae) caterpillars are specialist herbivores that feed on Dioon holmgrenii (Cycadacea). They are a well-documented case of chemical protection by sequestering cycasin and related compounds from their host. In this study we evaluated the effectiveness of aposematic defenses against chemical and visual invertebrate predators in wild populations of E. childrenae reared on D. holmgrenii. The results from field experiments indicated that the estimated survival and the intrinsic rate of increase in cohorts with predator exclusion were twice those in cohorts without predator exclusion. The visually oriented predators observed were Mischocyttarus wasps and assassin bugs, and the chemically oriented predators were Wasmannia, Crematogaster and Ectatomma ants. Other mortality factors observed were egg cannibalism, nuclear polyhedrosis virus and, reported for the first time, larval parasitism by fly larvae and a fungus. ResumenEficacia de las orugas aposemáticas de Eumaeus childrenae contra depredadores invertebrados en el medio natural. Las orugas de Eumaeus childrenae (Lepidoptera, Lycaenidae) son herbívoros especialistas que se alimentan de Dioon holmgrenii (Cycadacea). Constituyen un caso bien documentado de protección química mediante el secuestro de cicasina y de compuestos relacionados de su hospedante. En este estudio evaluamos la eficacia del aposematismo contra depredadores invertebrados con mecanismos químicos y visuales de caza en una población silvestre de E. childrenae criada en D. holmgrenii. Los resultados de los experimentos de campo indican que la supervivencia estimada y la tasa de cambio intrínseca fueron el doble en las cohortes con exclusión de depredadores que en aquellas donde no se excluyó a los depredadores. Los depredadores con mecanismos de caza visual observados fueron avispas del género Mischocyttarus sp. y chinches, mientras que los depredadores con mecanismos químicos de caza fueron varias especies de hormigas de los géneros Wasmannia, Crematogaster y Ectatomma. Otros factores de mortalidad observados fueron el canibalismo de huevos, el virus de la poliedrosis nuclear y el parasitismo de las larvas por larvas de moscas y un hongo, que se observan por primera vez.

Cycad phylogeny predicts host plant use of Eumaeus butterflies

“…Although Eumaeus–Zamia is an ideal system to study phylogenetic conservatism of larval host plant associations, there is a significant gap in natural history knowledge for species occurring in the southern distribution of the range of Eumaeus . The three northern species, Eumaeus childrenae , Eumaeus atala , and Eumaeus toxea are distributed from Florida to Mexico and have been widely collected and studied (see Contreras‐Medina et al, 2003 ; Jiménez‐Pérez et al, 2017 ; Koi & Daniels, 2015 , 2017 ; Koi & Hall, 2016 ; Martínez‐Lendech et al, 2007 ; Ruiz–García, 2020 ). The southern species, Eumaeus godartii , Eumaeus toxana , and Eumaeus minyas form a monophyletic lineage (Robbins et al, 2021 ) distributed from Costa Rica to Northern Bolivia, and are hereafter referred to as the “southern clade.” In contrast to the northern species, the larval host plants and geographical distributions of the southern clade are poorly known, and few studies on individual species have been conducted (Castillo‐Guevara & Rico‐Gray, 2002 , 2003 ; González, 2004 ; Santos Murgas & Abrego, 2016 ; Segalla et al, 2021 ; Taylor, 2020 ).…”

Cycad phylogeny predicts host plant use ofEumaeusbutterflies

“…Although Eumaeus – Zamia is an ideal system to test for phylogenetic conservatism of host plant associations, there is a significant gap in natural history knowledge for species occurring in the southern distribution of the range of Eumaeus . The three northern species, Eumaeus childrenae, Eumaeus atala , and Eumaeus toxea are distributed from Florida to Mexico and have been widely collected and studied (see (Contreras-Medina et al, 2003; Jiménez-Pérez et al, 2017; Koi & Daniels, 2015, 2017; Koi & Hall, 2016; Martínez-Lendech et al, 2007; Ruiz– García, 2020). The southern species, Eumaeus godartii, Eumaeus toxana , and Eumaeus minyas form a monophyletic lineage (Robbins et al, 2021) distributed from Costa Rica to Northern Bolivia, and are hereon referred to as the “southern clade.” In contrast to the northern species, the host plants and geographical distributions of the southern clade are poorly known, and few studies on individual species have been conducted (Castillo-Guevara & Rico-Gray, 2002, 2003; González, 2004; Santos Murgas & Abrego, 2016; Segalla et al, 2021; Taylor B., 2020).…”