Title
An ecological study of the relationship between two living fossils in Malawi: the Mulanje Tiger Moth (Callioratis grandis) and the Mulanje Cycad (Encephalartos gratus)
Author(s)
Bayliss, J.;Burrow, C.;Martell, S.;Staude, H.
Published
2010
Publisher
African Journal of Ecology
Abstract
The Mulanje tiger moth (Callioratis grandis) has recently been discovered feeding solely on the Mulanje Cycad, Encephalartos gratus. In its type locality Encephalartos gratus is severely threatened through habitat destruction and human population growth. As a result the first detailed demographic survey of Encephalartos gratus on Mount Mulanje was undertaken with particular emphasis on the relationship between E. gratus and Callioratis grandis. What is unusual about C. grandis is that the males exhibit lekking behaviour, for which aposematism may be a prerequisite. Cycads were surveyed in a systematic manner. Both the biotic and abiotic parameters were recorded from 532 wild Encephalartos gratus. Results showed the morphological range of measurements differed from that of previously published literature on this species. Results also showed that the incidence of Callioratis larval damage was related to the maturity of the wild cycads - moth damage was greater on more mature plants. Approximately 50% of surveyed cycads showed evidence of Callioratis moth damage, however, there was no apparent preference from the moth to select either male or female cycads as food plants for the larvae. In some cases there was severe damage to cycad fronds, but this did not seem to affect the production of reproductive cones or even the survival of individual cycads.Resume On a decouvert recemment que le papillon du Mulanje (Callioratis grandis) ne se nourrit que sur le cycadale Mulanje Encephalartos gratus. Dans son milieu type, Encephalartos gratus est gravement menace dans la nature a cause de la destruction de l'habitat et de la croissance de la population humaine. Par consequent, la premiere etude demographique detaillee d'Encephalartos gratus realisee sur le mont Mulanje fut entreprise en insistant particulierement sur la relation entre Encephalartos gratus et Callioratis grandis. Ce qui est inhabituel chez C. grandis, c'est que les males presentent un comportement territorial (lek). Les cycadales ont ete systematiquement surveillees. On a enregistre les parametres biotiques et abiotiques pour 532 Encephalartos gratus poussant dans la nature. Les resultats ont montre que l'amplitude des mesures morphologiques differait de ce que la litterature existante decrit sur cette espece. Ils ont aussi montre que l'incidence des dommages causes par les larves de Callioratisetait liee a la maturite des cycadales sauvages - les degats causes par les papillons etaient plus graves sur les plants plus matures. Environ 50% des cycadales suivis montraient des traces de dommages causes par ce papillon, mais il n'y avait pas de preuve qui aurait pu montrer que le papillon selectionnait des cycadales males ou femelles pour en nourrir ses larves. Dans certains cas, il y avait des degats serieux dans les feuilles de cycadales; cependant, cela ne semblait pas affecter la production de cones reproducteurs, pas plus que la survie des individus.
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PUB13357