Importance of Dominican Republic amber for determining taxonomic bias of fossil resin preservation—A case study of spiders

Abstract

Fossils preserved in amber represent only a small fraction of the biota which was alive in the amber forest. In order to make accurate palaeoenvironmental reconstructions, it is necessary to determine the biases which affect preservation. Only the Baltic and Dominican Republic amber deposits have had inclusions described in sufficient quantities suitable for quantitative analyses. Baltic amber is twice the age of Dominican, with a correspondingly higher proportion of extinct supraspecific taxa, and was produced in a climate very different to that in the region today. Dominican Republic amber was formed in a tropical climate similar to that in the region today and many of the preserved spider supraspecific taxa are extant. Therefore, the fossil and Recent Hispaniolan faunas are directly comparable ecologically. Spiders (extinct and extant) are significantly more diverse than other groups for which Hispaniolan species diversity data are available. Thus, they form an ideal model for assessing taxonomic bias of Dominican amber preservation. This is the first time that taxonomic richness estimates have been made and compared quantitatively between extant and fossil amber faunas. Extant and extinct (Dominican Republic amber) Hispaniolan spiders are compared at family level. Overall, the two faunas are similar but some distinct differences are apparent. Hispaniolan representatives of the families Cyrtaucheniidae, Microstigmatidae, Ochyroceratidae, Palpimanidae, Tetrablemmidae, Agelenidae, Anapidae and Mysmenidae are known only from amber, whereas Drymusidae, Deinopidae, Desidae, Amaurobiidae, Prodidomidae and Zoridae are known only from the extant fauna. Many families have similar fossil and extant species diversities. Oonopidae and Dictynidae are significantly more diverse in amber. Many families currently known only from Dominican amber probably have undiscovered extant species on Hispaniola. Family species richness estimates were calculated for both fossil and extant spider faunas, but only those for the extant fauna provide results consistent with a neotropical spider assemblage. Fossil richness estimates were excessively high as a result of the large number of singletons. Nevertheless, the Dominican Republic is the only place on Earth where fossils in amber occur in sufficient numbers and that are closely related to the extant fauna, such that direct diversity/ecological comparisons can be made. Given future research directed at identifying spiders and other inclusions in the large amber collections amassed in Museums around the world, detailed comparisons of these faunas will allow us to better determine taxonomic biases associated with amber preservation.