See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/233696987 How many species are there in Bermuda? Article in Bulletin of Marine Science -Miami- · May 1998 CITATIONS READS 24 105 1 author: Wolfgang Sterrer Bermuda Natural History Museum 81 PUBLICATIONS 1,841 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: the roots of eukaryotes, sex, and cancer View project Gnathostomulida of the world View project All content following this page was uploaded by Wolfgang Sterrer on 24 November 2014. The user has requested enhancement of the downloaded file. BULLETIN OF MARINE SCIENCE, 62(3): 809–840, 1998 HOW MANY SPECIES ARE THERE IN BERMUDA? Wolfgang Sterrer ABSTRACT Explored since 1515 and documented in at least 3000 publications, Bermuda’s natural history is well enough known to permit a first biodiversity inventory similar to one being conducted in Hawaii. Although seamount Bermuda originated 110 mya and was “topped up” by a separate volcanic event 33 mya, its extant biodiversity was largely shaped by pleistocene sea level fluctuations which alternately favored terrestrial and shallow ma- rine biota. It was more recently molded by cataclysmic episodes of species extinction and introduction brought about by human colonization, several of which occurred only in the past half century. A taxonomic tabulation of Bermuda’s species, in comparison with Ha- waii, reveals that Bermuda now has at least 8299 species of which 4597 are marine and 3702 are terrestrial. Hawaii, which has 2.68 times more species, has an overall endemism rate of 38.0%, more than ten times that of Bermuda (3.0%). While the degree of marine endemism is 11.8% in Hawaii vs. only 2.4% in Bermuda, the difference is even higher in terrestrial taxa (48.3% vs. 3.7%), especially in Lichens (33.2% vs. 10.9%), Bryophytes (24.1% vs. 4.0%), Ferns (60.5% vs. 15.8%), Angiosperms (44.5% vs. 1.0%), Gastropoda (91.3% vs. 23.4%) and Insecta (65.9% vs. 3.4%). The tabulation of major taxa is accom- panied by notes on the occurrence and fate of selected species, and an extensive bibliog- raphy. Bermuda’s nature—50 km2 of rolling hills amidst 750 km2 of shallow coral reef—has been a topic of wonderment and study at least since 1609, when the first settlers-to-be fell upon an island with “strange, darke and cumbersome Caues,” with “Sea Fowle in great numbers, that lyeth in little holes in the ground, like unto Coney holes,” and “fish [very fat and sweete], and so abundant, that if a man steppe into the water, they will come round about him: so that men were faine to get out for feare of byting” (Lefroy, 1877). Such was the naive, native richness of life when first encountered by human explorers on all but the most forbidding oceanic islands. But alas! awe soon gave way to exploitation, and only a few years later Bermuda made history by issuing the first conservation laws in the New World, “against the spoyle and havocke of the cahows and other birds” (1616), and “against the killing of over young tortoises [turtles]” (1620). As is probably also true for most modern conservation legislation, it came too late to be effective. Bermuda is no longer a sea turtle rookery, and the endemic petrel, Pterodroma cahow, is on the verge of extinc- tion (Wingate, 1981). Growing awareness, from the 1970s on, that the world’s biodiversity, although an order of magnitude greater than previously estimated, is rapidly shrinking (Ehrlich, 1981; Wil- son, 1988) coincided with the realization that human well-being depends critically on the free ecosystem services which only a healthy environment can provide (Costanza, 1991). Almost inevitably, islands took center stage again, not only as natural laboratories for evolution (Darwin, 1860) and ecological dynamics (MacArthur and Wilson, 1967), but with a new emphasis on anthropogenic effects and conservation. The myth that prehis- toric island colonizers lived in harmony with nature soon gave way (Diamond, 1988) to the conclusion that “a human-caused ‘biodiversity crisis’ began thousands of years ago and has nearly run its course”, resulting, for instance, in the extinction of 2000 bird spe- 809 810 BULLETIN OF MARINE SCIENCE, VOL. 62, NO. 3, 1998 cies in the tropical Pacific alone, or 20% of the world’s bird diversity (Steadman, 1995). The sudden collapse of Jamaica’s coral reef system and fisheries (Hughes, 1994) due to overfishing and development, and the tragedy played out at this very time (Camhi, 1995) in the Galapagos, an archipelago that has come to symbolize the fragile tenacity of life more than any other place on earth, together make an urgent case for learning as much as can be learned about the components and dynamics of our island ecosystems. BERMUDA’S NATURAL HISTORY The Island’s natural history has been recorded since 1515 in at least 3000 documents consisting of historical references (see Lefroy, 1877), books, journal articles, graduate theses, unpublished student reports and informal notes in local news media. Pioneering contributions are by Jones (1859), Goode (1876), Jones and Goode (1884), Heilprin (1889), Agassiz (1895), Hurdis (1897), and especially Verrill (1902, 1907) who provided the most comprehensive biogeological inventory of the Island. Additional monographs are by Britton (1918), Beebe and Tee-Van (1933), and Waterston (1947). Hayward et al. (1981) drew attention to the delicate balance between people and resources in an oceanic island environment. More recently, preparations for a comprehensive field guide (Sterrer, 1986) prompted a number of authors to revisit Bermuda’s marine biota. Iliffe (1993) discovered an unexpected treasure trove in Bermuda’s drowned caves that yielded 66 new records representing 2 new orders, one new family, 14 new genera and 60 new species, a list that may well contain a major portion of Bermuda’s endemics. Wingate (1959) and Amos (1991) catalogued birds, and Hilburn (in prep.) orchestrated an inventory of the Island’s terrestrial arthropods (Hilburn, 1989; Hilburn and Gordon, 1989; Hilburn, 1990; Gordon and Hilburn, 1990; Stoetzel and Hilburn, 1990; Wilson and Hilburn, 1991; Henry and Hilburn, 1990; Hodgson and Hilburn, 1991; Ferguson, Hilburn and Wright, 1991; Woodley, 1996). Checklists of Bermuda’s marine algae (Schneider), earthworms (Reynolds), echi- noderms (Pawson and Devaney), fishes (Smith-Vaniz et al.), and terrestrial (Slapcinsky and Bieler) and marine mollusks (Jensen) are in preparation. This paper began 25 yrs ago, as a collection of loose notes on anything that struck me as remarkable about the marine fauna and flora of Bermuda (Sterrer, 1986). It gained impetus from anecdotal evidence that I worked into a semi-popular book on Bermuda’s marine life (Sterrer, 1992), and borrowed its final title from the Hawaii Biological Survey (Eldredge and Miller, 1995), in the hope that this will contribute to the standardization and comparability of island biodiversity inventories. With apologies to Eldredge and Miller, therefore, and with their cautions regarding the preliminary nature and patchiness of the product, this paper summarizes Bermuda’s physiography and geological history, presents a table of numbers of species known to make up the Bermudian biota, adds notes and anecdotes regarding the tabled taxa, and concludes with a biodiversity comparison be- tween Hawaii and Bermuda. BERMUDA TODAY Located at 32°18'N, 64°46'W, Bermuda is a crescent-shaped chain of about 150 islands of which the seven main ones are now interconnected by bridges or causeways. Only 35 km long and 3 km at its widest, Bermuda is moderately hilly (highest elevation 79 m), STERRER: HOW MANY SPECIES ARE THERE IN BERMUDA? 811 with an habitable land area of about 50 km2. Bermuda is subtropical, with mean monthly sea surface temperatures ranging from 18° to 28°C, air temperatures from 19° to 30°C, an annual average humidity of 77% and rainfall of 146 cm (Morris et al., 1977; Hayward et al., 1981). There are no surface streams, fewer than 20 brackish and freshwater ponds, and in only 20% of the land area the seawater-permeated limestone supports a shallow fresh- water lens (Morris et al., 1977). Bermuda’s now has a population of nearly 60,000 and is visited annually by almost half a million tourists, which makes it one of the most densely populated countries in the world. If it were not for its nature reserves, Bermuda might be described as a “suburb without a city” verging on “a city without a country” (D. B. Wingate, pers. comm.). BERMUDA’S GEOLOGY—IN A GRAIN OF SAND A simplified geological history of Bermuda begins with a 2000 m high seamount aris- ing on the Mid-Atlantic Ridge about 110 mya and drifting westward on the North Ameri- can Plate. A separate volcanic hot-spot event some 33 mya (Aumento and Sullivan, 1974) “topped up” the eroded seamount, creating three peaks of which the northeastern-most and largest forms the Bermuda pedestal; the two smaller ones to the southwest, now 60 m below sea level, are called Argus and Challenger Banks. Truncated just below present sea level as a result of erosion, Bermuda’s volcanic pedestal is entirely covered by a +75 m thick limestone cap which formed in the Pleistocene (10,000 to 1.6 mya). During warm periods (e.g., 125,000 and 200,000 yrs ago), sea levels were at least 5 m above today’s, coral reefs flourished, and vast wind-blown (aeolian) dunes of carbonate sand accumu- lated. In cold periods (e.g., 20,000 yrs ago), sea levels dropped as much as 125 m below today’s and reef growth stagnated; sand dunes solidified and acquired a soil cover (paleosol), and caves formed within the sand stone.