Biodiversity and Biogeography of Polychaetes (Annelida): Globally and in Indonesia

Abstract

This thesis presents a review of the biodiversity of polychaete worms (Annelida) and their distribution across the globe. It also provides an evaluation of polychaete biodiversity studies in Indonesia and a description of a new polychaete species collected from Ambon Island, Province of Maluku, Indonesia. I reviewed polychaete data from the World Register of Marine Species (WoRMS), and found that 11,456 accepted polychaete species (1417 genera, 85 families) have been formally described by 835 first authors since the middle of the 18th century. A further 5200 more polychaete species are predicted to be discovered by the year 2100. The total number of polychaete species in the world by the end of the 21st century is thus anticipated to be about 16,700 species. While the number of both species and authors increased, the average number of polychaete species described per author decreased. This suggested increased difficulty in finding new polychaete species today as most conspicuous species may have been discovered. I analysed polychaete datasets from the Global Biodiversity Information Facility (GBIF), the Ocean Biogeographic Information System (OBIS), and my recently published checklist of Indonesian polychaete species, and identified 11 major biogeographic regions of polychaetes. They were: (1) North Atlantic & eastern and western parts of the Mediterranean, (2) Australia, (3) Indonesia, (4) New Zealand, (5) the Atlantic coasts of Spain and France, (6) Antarctica and the southern coast of Argentina, (7) Central Mediterranean Sea, (8) the western coast of the USA, (9) the eastern part of the Pacific Ocean, (10) Caribbean Sea and (11) Atlantic Ocean. Further, the latitudinal species richness gradient pattern of the animals was found to be asymmetrically bimodal, with similar peaks of richness in the northern (60oN) and southern (30oS) hemispheres, and a pronounced dip north of the Equator (15oN). The pattern is unlikely to be due to sampling bias, but rather a natural phenomenon most significantly correlated with sea temperature. I garnered all Indonesian polychaete species names from taxonomic and ecological literature, as well as from GBIF and OBIS, and found that since the middle of the 18th century, 713 polychaete species (55 families) have been identified from the Indonesian waters. Of these, 301 species (40 families) were described from the geographic region. Through time, most polychaete samples were collected during the Siboga Expedition at the turn of the 19th century, most of which were identified by European taxonomists and deposited in museums in the Netherlands, but now centralised at the Naturalis Biodiversity Center, Leiden. Marine benthic studies conducted by local scientists have yielded polychaete specimens, yet most were not identified to species level and not vouchered in a recognised institution. I discovered that the polychaete collections at the three largest polychaete repositories in Indonesia were mostly unidentified, unpublished, and not databased, suggesting that the taxonomic study of the polychaete fauna, at least locally, has been largely overlooked. I collected polychaete specimens from the Wallacea region and its surrounding waters, and discovered a new capitellid species formally named Capitella ambonensis Pamungkas, 2017. The species, which was discovered from a mangrove habitat on Ambon Island, differs from other Capitella species in the form of hooded hooks and the methylene blue staining pattern. Indeed, the polychaete material obtained from this fieldwork may contain more new species and may give a clue as to whether or not the Wallace’s Line is a real boundary for polychaete fauna.