Coextinction and recognition for unloved threatened species

I love this quote from Bob May (1986) – “to a good approximation, all species are insects”. Mark Burgman and David Lindenmayer’s (1998) book communicates that point beautifully, with an illustration by Kate Thompson in which the size of the organisms is approximately proportional to the number of species in that group.

Approximately two-thirds of species in the world are thought to be insects, while vertebrates make up a tiny fraction (probably less than 1%). If insects and vertebrates had the same extinction risk there should be about 100 times as many threatened insects as vertebrates, but insects are relatively rare in threatened species lists.

Given the paucity of insects in threatened species lists, one might think that they are somehow extremely robust to extinction. Of course, that discrepancy is simply a function of the attention they have received. Species are only listed when there is sufficient information to assess them. Insects and other invertebrates, while loved by some, get much less attention than their abundance, biomass and functional roles deserve.

One of our QAEG post-docs, Melinda Moir, is doing her bit to redress the imbalance. Mel is studying the co-extinction risk of invertebrates that depend on threatened plants (e.g., Moir et al. 2010, 2011, in press a, in press b). As part of her previous research on insects, Mel and Gary Taylor identified some new psyllid species, one of which, Vesk’s plant louse Acizzia veski (Taylor and Moir 2009), has just been listed as vulnerable in Western Australia. Yes, it is a sapsucker, but not the yellow-bellied version, I believe.

One of the interesting things is that it is the first insect to be listed in Australia (perhaps more widely?) as threatened on the basis of co-extinction risk, being an affiliate of the threatened plant Acacia veronica, which is restricted to the Stirling Range near Albany in Western Australia. Co-extinction, the extinction of a species resulting from a decline of its host, is seen as a major threat to biodiversity (Koh et al. 2004), so it is interesting that co-extinction figured prominently in the listing of A. veski.

Another interesting aspect is that the species in question, Acizzia veski, has the honour of being named after one of QAEG’s principal researchers Peter Vesk. Now I’m sure the naming has nothing to do with any similarity of appearance or behaviour.

Photo credit for A. veski: Gary Taylor

But the common naming is rather appropriate because Peter is the primary author of a paper that describes a method to estimate host breadth, which is an important aspect when assessing co-extinction risk (Vesk et al. 2010).  One of the key features of this paper is that it accounts for imperfect detection of affiliate species on their hosts, providing a probability distribution for both the number of affiliates per host species, and the number host species per affiliate. QAEG has a range of research in the area of detectability, some of which is described in previous posts.

Edit (13 June 2013): For a recent post along similar lines (focusing on parasites of animals), check out Parasites: the cinderellas of wildlife conservation by Haylee Weaver.

References (please email me if you need copies of our papers)

Burgman, M.A., and Lindenmayer, D.B. (1998). Conservation biology for the Australian environment. Surrey Beatty, Australia.

Koh, L.P. et al. (2004). Species coextinctions and the biodiversity crisis. Science 305, 1632-1634.

May, R.M. (1986). Biological diversity: How many species are there? Nature 324, 514 – 515.

Moir, M.L., Vesk, P.A., Brennan, K.E.C., Hughes, L., Keith, D.A., McCarthy, M.A., Coates, D.J., and Barrett, S. (in press a). A preliminary assessment of changes in plant-dwelling insects when threatened plants are translocated. Journal of Insect Conservation.

Moir, M.L., Vesk, P.A., Brennan, K.E.C., Keith, D.A., Hughes, L., and McCarthy, M.A. (2010). Current constraints and future directions in estimating coextinction. Conservation Biology 24: 682-690.

Moir, M.L., Vesk, P.A., Brennan, K.E.C., Keith, D.A., McCarthy, M.A., and Hughes, L. (2011). Identifying and managing threatened invertebrates through assessment of coextinction risk. Conservation Biology 25: 787-796.

Moir, M.L., Vesk, P.A., Brennan, K.E.C., Poulin, R., Hughes, L., Keith, D.A., McCarthy, M.A., and Coates, D.J. (in press b). Considering coextinction of dependent species during ex situ conservation and assisted migrations of threatened hosts. Conservation Biology.

Vesk, P.A., McCarthy, M.A., and Moir, M.L. (2010). How many hosts? Modelling host breadth from field samples. Methods in Ecology and Evolution 1: 292-299.

Taylor, G.S., and Moir, M.L. (2009). In threat of co-extinction: two new species of Acizzia Heslop-Harrison (Hemiptera: Psyllidae) from vulnerable species of Acacia and Pultenaea. Zootaxa 2249: 20-32.

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About Michael McCarthy

I conduct research on environmental decision making and quantitative ecology. My teaching is mainly at post-grad level at The University of Melbourne.
This entry was posted in CEED, Detectability, Probability and Bayesian analysis and tagged , , , , , , . Bookmark the permalink.

5 Responses to Coextinction and recognition for unloved threatened species

  1. Pingback: The yellow-bellied sapsucker & I | Michael McCarthy's Research

  2. Pingback: Unloved biodiversity and coextinction | Michael McCarthy's Teaching

  3. Pingback: On triage, public values and informed debate: trade-offs around extinction | Quantitative & Applied Ecology Group

  4. For more on the importance of invertebrates, check out the article on The Conversation by Kylie Williams: Ignoring Invertebrate Conservation is Simply Spineless

  5. Pingback: Conservation triage, and how the public values species | Michael McCarthy's Research

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