Ant sex keeps getting weirder

In 2008 Jürgen Heinze penned “The Demise of the Standard Ant“, noting that the stereotyped ant nuclear family (one queen, one male, and lots of kids) was increasingly obscured by an accumulation of myrmecological data showing enormous variation among species in life history, that real ant colonies were often messy polygamous affairs, and that odd strategies like clonal reproduction were probably more common than previously thought.

Paratrechina longicornis, the black crazy ant

A study out today by Pearcy et al reveals that a common invasive ant, Paratrechina longicornis, is one of those oddballs:

from the abstract:

We discovered that the highly invasive longhorn crazy ant, Paratrechina longicornis, has evolved an unusual mode of reproduction whereby sib mating does not result in inbreeding. A population genetic study of P. longicornis revealed dramatic differences in allele frequencies between queens, males and workers. Mother–offspring analyses demonstrated that these allele frequency differences resulted from the fact that the three castes were all produced through different means. Workers developed through normal sexual reproduction between queens and males. However, queens were produced clonally and, thus, were genetically identical to their mothers. In contrast, males never inherited maternal alleles and were genetically identical to their fathers. The outcome of this system is that genetic inbreeding is impossible because queen and male genomes remain completely separate.

In other words, the DNA of males and queens are separate clonal lineages, while workers are hybrids between the two. This arrangement avoids the inbreeding problems associated with diploid males, possibly helping this species colonize new sites from small propagules.

What’s more, P. longicornis is not the only invasive ant with this reproductive quirk. Wasmannia auropunctata, the little fire ant, shares a similar system, suggesting that clonal reproductives and hybrid workers may be a more general strategy of invasive social insects.

For a better explanation than mine (as usual), Ed Yong has more.

Pearcy, M. et al 2011. Sib mating without inbreeding in the longhorn crazy ant. Proc. R. Soc. B, Published online before print February 2, 2011, doi:10.1098/rspb.2010.2562

10 thoughts on “Ant sex keeps getting weirder”

  1. Pingback: Anonymous

  2. So in other words, males arise directly from the genetic material of their father’s sperm, which are identical. But how do sperm cells, which are essentially mobile nuclei, able to directly become whole organisms without the resources of the egg? Wouldn’t this also entail that there is only a small set number of male lineages in this entire species, and that number can theoretically only get smaller as certain lineages go extinct without being replaced by new male lines?

    Also I’m speculating that this trait will be found to be frequent in invasive species where alates can mate inside the nest. Is that a reasonable prediction?

  3. Insect sex in general is wierd, heh. Facultative parthenogenesis all over the place, cyclical parthenogenesis in aphids, “traumatic” insemination in bedbugs, ripping off heads in mantids, new sexual pheromone systems in leaps rather than in minute stages, and so on.

    This certainly is an interesting twist.

  4. Jason C.: “But how do sperm cells, which are essentially mobile nuclei, able to directly become whole organisms without the resources of the egg?”

    This is a crucial question! I remember that in another instance (was it Wasmannia auropunctata?) a fraction of the sperm cells after penetrating an egg cell will kill or eliminate the egg nucleus (resp. its haploid genome). The egg then can develop like an ordinary non-fertilized egg into a male, but the mother’s genome has been replaced by that of the “father”.
    Most sperm however would combine with the egg nucleus, and ordinary diploid workers would be formed in the instance of Paratrechina.
    I wonder whether this has been discussed in the original article.

    1. It would be interesting to investigate the factors that regulate egg hijacking vs. fertilization…this could have impacts for our currently messy cloning techniques. Perhaps one day we could slip a donor nucleus into a donor egg without having to extract the egg’s nucleus first.

      1. Given ants known domestication of bacteria and fungi, I would not put it past their capability to domesticate a virus involved in this job. lol

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