Malawi cichlids – how aggressive males create diversity

Blogging on Peer-Reviewed ResearchCertain groups of animals show a remarkable capacity for quickly evolving into new species to seize control of unexploited niches in the environment. And among these ecological opportunists, there are few better examples than the cichlids, a group of freshwater fishes that are one of the most varied group of back-boned animals on the planet.

Malawi cichlidsIn the words of Edward O. Wilson, the entire lineage seems “poised to expand.” The Great Lakes of Africa – Tanganyika, Malawi and Victoria – swarm with a multitude of different species; Lake Malawi alone houses over 500 that live nowhere else in the world.

All of these forms arose from a common ancestor in a remarkably short span of time. Now, a new study suggests that this explosive burst of diversity has been partly fuelled by rivalry between hostile males.

Michael Pauers of the Medical College of Wisconsin found that male cichlids have no time for other males that look like them and will bite, butt and threaten those who bear the same colour scheme. In doing so, they encourage diversity in the lake since mutant males with different tints are less likely to be set upon by territorial defenders.

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New plant species arise from conflicts between immune system genes

Plants from the same species can fail to breed together because incompatible genes from the parents cause the offspring’s immune system to fatally turn on itself. These conflicts between otherwise normal genes could split groups of the same plant into separate species.

Hybrid necrosis in Arabidopsis is the result of clashing immune system genes“Congratulations, it’s a stunted, malformed, necrotic hybrid!” Those aren’t really the words that new parents want to hear but thankfully, plants aren’t in a position to be that upset.

In several species of plants, a surprising number of offspring turn out to be malformed hybrids that quickly wither and die. Now, Kirsten Bomblies and colleagues from the Max Planck Institute for Developmental Biology have found out why.

Two genes, one passed down by each parent, ignite an reaction in the hybrid youngster that turns its immune system against it. It’s not a genetic disorder; neither gene was faulty and both were harmless in their native parental environments. But they evolved apart from each other and make poor bedfellows when united.

They behave like employees from two merging companies. Having developed in different backgrounds and working cultures, they can find it difficult to work together, lowering the productivity of the new business.

Over time, these incompatibilities could drive wedges between different plant strains, reducing their chances of successful mating and turning separate strains into separate species.

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