Factors influencing when species are first named and estimating global species richness

Abstract

a b s t r a c tEstimates of global species richness should consider what factors influence the rate of species discovery at global scales. However, past studies only considered regional scales and/or samples representing <0.4% of all named species. Here, we analysed trends in the rate of description for all fish species (2% of all named species). We found that the number of species described has slowed for (a) brackish compared to marine and freshwater species, (b) large compared to small sized fish, (c) geographically widespread compared to localised, (d) species occurring in the tropics and northern hemisphere compared to southern hemisphere, and (e) neritic (coastal) species compared to pelagic (offshore) species. Most (68%) of the variation in year of description was related to geographic location and depth, and contrary to expectations, body size was a minor factor at just 6% (on a standardised scale). Thus most undiscovered species will have small geographic ranges, but will not necessarily be of smaller body size than currently known species. Accordingly, global assessments of how many species may exist on Earth need to account for geographic variation.

Dynamics of global institutional collaboration in insect taxonomy reveal imbalance of taxonomic effort

“…). Previous studies also showed the increase in species descriptions from Asia and South America may result from the increasing number of researchers describing new species, which is likely due to the growth of new scientific positions in Asia and South America in recent past years (Costello et al ., , , ). Developing countries have maintained a good upward trend in the insect taxonomy field, but some developed countries are still ahead in certain areas.…”

The hidden half: ecology and evolution of cryptobenthic fishes on coral reefs

“…Marine fishes are integral to a variety of critical ecosystem processes and provide many ecosystem goods and services (Mora, 2015). Despite this, the relatively recent exploration of the world's oceans, along with present-day challenges associated with sampling in the marine environment, have left many aspects of marine fish biodiversity unexplored (Mora, Tittensor & Myers, 2008;Costello et al, 2015). Despite occupying only a fraction of the marine biome, tropical coral reefs harbour approximately one third of global marine fish biodiversity (Spalding & Grenfell, 1997).…”

Extinct, obscure or imaginary: The lizard species with the smallest ranges

“…Several studies have tried to link range size to biological attributes such as body size (e.g., Agosta & Bernardo, 2013) or to geographic attributes such as latitude (Rapaport's Rule; Ruggiero & Werenkraut, 2007). A common finding, however, associates range size not with particular biological attributes, but with the year, a species was described (e.g., Costello, Lane, Wilson, & Houlding, 2015;Gaston, Blackburn, & Loder, 1995). Generally, scientists observed, distinguished and described the widely distributed species early.…”

“…Generally, scientists observed, distinguished and described the widely distributed species early. In fact, range size consistently emerges as the key correlate of description date in all tests we know that examined this link (e.g., Collen, Purvis, & Gittleman, 2004;Colli et al, 2016;Costello et al, 2015;Diniz-Filho et al, 2005). Species that were discovered and described (as opposed to being split from other species) relatively recently are poorly known almost by definition, given that not enough time has lapsed for biologists to study their biology, abundance and true range extent.…”