Evolution on a shaky piece of Gondwana: is local endemism recent in New Caledonia?

Abstract

New Caledonia is well known as a hot spot of biodiversity whose origin as a land mass can be traced back to the Gondwanan supercontinent. The local flora and fauna, in addition to being remarkably rich and endemic, comprise many supposedly relictual groups. Does the New Caledonian biota date back to Gondwanan times, building up its richness and endemism over 100 Myr or does it result from recent diversifications after Tertiary geological catastrophic events? Here we use a molecular phylogenetic approach to answer this question with the study of the Neocaledonian cockroach genus Angustonicus belonging to the subfamily Tryonicinae from Australia and New Caledonia. Both geological and molecular dating show that the diversification of this group is less than two million years old, whatever the date of its origin itself. This dating is not consistent with hypotheses of Gondwanan richness and endemism in New Caledonian biota. In other terms, local richness and endemism at the specific level are not necessarily related to an old Gondwanan origin of the Neocaledonian groups. © The Willi Hennig Society 2005.

New Caledonia: a very old Darwinian island?

“…A stronger argument than one based on molecular clocks alone can be made when a clade of microendemic species in New Caledonia is sister to species occurring only on recently uplifted neighbouring islands ( Norfolk, Lord Howe), which, as mentioned above, is the case for Araucaria trees (Setoguchi et al 1998) and Placostylus land snails (Trewick et al in press). Another case is the cockroach Angustonicus, two species of which occur only on the Loyalty Islands and are sister to all those on the New Caledonia mainland (Murienne et al 2005). As argued by Murienne et al (2005), this kind of relationship between taxa of the New Caledonia mainland and of a neighbouring and more recent island is good evidence for recent diversification in each group since sister groups are the same age, i.e.…”

“…However, recent phylogenetic studies provide some insight into microendemism patterns and their causes. Microendemism appears primarily related to allopatric speciation in plants (Eibl et al 2001;Swenson et al 2001Swenson et al , 2007Bartish et al 2005;Bottin et al 2005;Tronchet et al 2005), insects (Desutter- Murienne et al 2005, in press a), land snails ( Trewick et al in press) and lizards (Bauer & Sadlier 2000;Bauer et al 2006;Smith et al 2007), even though some cases of sympatry and even syntopy have also been documented in diving beetles (Balke et al 2004(Balke et al , 2007b.…”

“…First, more than 20 Ma of total submersion from the Palaeocene to the Eocene make it difficult to retain the notion that a Gondwanan biota has survived locally (Murienne et al 2005;Murienne 2006;Pelletier 2006). Even if this biota persisted on emerged lands in the region, the occurrence of which is speculative, they had to disperse back to New Caledonia in the Oligocene.…”

“…Another example is the radiation of the cricket genus Agnotecous ( Eneopterinae), which includes many species with peculiar stridulatory apparatuses that emit songs in unusually high frequencies and with harmonic shifts (Robillard & Desutter-Grandcolas 2004;Robillard et al 2007). The cockroach subfamily Tryonicinae (Blattidae) includes the speciose genus Lauraesilpha, the members of which exhibit a unique combination of Araucaria (Setoguchi et al1998) Angustonicus (Murienne et al 2005) geckos (Bauer et al 2006) Sapotaceae (Bartish et al 2005) Proteaceae (Barker et al 2007) Paratya (Page et al 2005) diving beetles (Balke et al 2007a, b) galaxiid (Waters et al 2000) Tasmantis Scincidae (Smith et al 2007) sandalwoods ( behavioural traits, wood eating, intestinal ciliates and solitary habits (Grandcolas 1997;Murienne 2006; in press a, submitted). These characteristics recall those of panesthiine cockroaches (Blaberidae), which include many wood-eating species in Australasia and throughout the southwest Pacific (including Vanuatu and Lord Howe Islands), but with the exception of New Caledonia (Roth 1991).…”

“…Morat 1993b). This Gondwanan view became widespread during the past few decades (Lowry 1998;Lowry et al 2005;Murienne et al 2005) and has often been invoked as a reason to study the diverse New Caledonian biota (e.g. Mittermeier et al 1996;Pagel 2003).…”