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The human as a speciating force of nature!

By JW Dowey - 02 Jul 2016 9:50:0 GMT
The human as a speciating force of nature!

This is the enormous 19cm (7.5”) wingspan of a damselfly from Costa Rica, instantly recognisable by one (female) or 2 (male)white spots, speciating rapidly in the dwindling forests, as there has been a long term failure to establish wildlife corridors for it to dash along! Giant damsel image

Credit: © Wiki CC, in the form of Steven G Johnson

While we are warming the planet, how have other species been affected, not only by the heat, but also our other disruptive ways? Speciation has famously been driven by man (or woman) in animals such as domestic birds and mammals, but what about the others which live around humans. Maybe the peregrine falcon of many cities has changed from the rural raptor, or has the pigeon diet and “cathedral-influenced” genotype and phenotype. Similar change will certainly result from hunting and fishing activity by our species.

One study on the rate of change in these harvested populations of animals increased threefold. Plaice and cod phenotypes have been heavily influenced by overfishing, especially of older and larger individuals. If you want obvious and terrestrial evidence, it can be found in poached elephant populations, bighorn sheep in North America and elk/deer, as well as your typical garden snails! But the key is to find documented speciation in one of these, or a plant species and this is what is being done, albeit slowly. Human habits typically isolate populations of species, whether through domestication or the lack of provision of wildlife corridors. The causes of any speciation could be predominantly human and partly natural or vice-versa. Finding the direct link causing the speciation is the trick!

The Global Invasive Species Database provides some simple solutions of IAS (Invasive Alien Species) that penetrate new habitats and adapt accordingly. 70% of introduced plant species change in morphologies such as height while fish like guppies (Poecilia reticulata) alter their age of maturation after 11 years in a new site. It is also likely but not proved that hybrids have been formed many times as humans transport species like these even from geographically-close habitats.

Domesticated animals such as the multi-variants of the dog species, and 474 others, have followed humans over 11,000 years at least. New species have not been formed, except where mating is impossible, but the trait development required for such evolution is blatant. In plant species, novel crops have been formed in at least 6-8 hybrid species such as in wheat and various cabbages, where the full definition of a new species should be correct. Less pleasant are the hangers-on to human communities, in which we can see the evolution of a true species of London Underground mosquito. Warm and safe in the vast subterranean network, this novelty can’t interbreed with above-ground Culex pipiens. We think the name Culex piccadillii (HINT) could be appropriate, but the widespread blighter is currently classified as Culex pipiens molestus.

The noted lack of corridors has fragmented forest populations of the giant damselfly, Megaloprepus caerulatus in America (from Costa Rica to Mexico) causing reproductive incompatibility. But equally well, new habitats and even new technologies can function as speciating agents, with hydropower systems forcing some fish to stop their migrations and genetically modified organisms likely to create new entities that could rapidly speciate. The whole problem of microorganisms, whether resisting our puny antibiotic attacks, or colonising space vehicles, is almost a series (or yet another novel) in itself.

It is difficult in current science to assess whether we are detractors from speciations or whether we are encouraging these intrepid organisms in various cases. The authors of this eye-opening paper are JW Bull and Martine Maron of the Universities of Copenhagen and Queensland. They publish How humans drive speciation as well as extinction in the Proceedings of the Royal Society B.