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I have been reading about eusocial species and have some questions. What is the basis for caste differentiation? Is it entirely genetic? Does the queen have the code for soldiers, workers etc in her own genes, so only a mutation to the queen results in change of the whole colony's castes? As a related question, how do different castes evolve?

It seems to me that if only one individual in a colony is reproducing, the rate of evolution must necessarily be much slower because any genetic change in the queen would affect all castes, which is likely to have some negative effects.

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  • $\begingroup$ please rephrase: prevent stagnating evolutionary. casts just have a group fitness impact, I don't understand what you mean. $\endgroup$ – com.prehensible Oct 18 '17 at 17:32
  • $\begingroup$ I think this is a great question (and if I have time I'll attempt an answer later) but it had some issues, so I've attempted to rewrite it more clearly. If you feel it no longer reflects what you wanted to ask please revert it; I won't be offended :) $\endgroup$ – arboviral Oct 18 '17 at 18:50
  • $\begingroup$ (I'd also suggest adding some more information about the reading you've done so far.) $\endgroup$ – arboviral Oct 18 '17 at 18:51
  • $\begingroup$ @arboviral: Thanks for the edit, As far as I understand the edit, it still represents my intend. And what I read so far... well, the linked wiki article. $\endgroup$ – Zaibis Oct 19 '17 at 8:08
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Does a fertile queen have the code for soldiers/workers in its own genes, so only a mutation to the queen results in change of the whole coloniy's castes?

Yes.

But how that would protect them from just going extinct due to one unfavorable mutation to a queen?

One unfavorable mutation to a queen could make that queen and her lineage "extinct". It wouldn't necessarily have any effect on the rest of the population (i.e. other queens and their lineages). There's no difference here between eusocial and other species.

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  • $\begingroup$ that's totally right, although you may add that the queen can be inseminated by many males and the nuptial flights may have individuals of a wide range genetically. a proportion of the new queens may have the defective gene omitted or complemented via egg fertilization. $\endgroup$ – com.prehensible Oct 18 '17 at 18:21
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Ants are eusocial and close relatives of bees and wasps. Ant and bees use Haplodiploidy. it is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid.

Young queen ants leaving the nest can have one or 10 or 20 fathers. The new queens and workers are not necessarilly clones, and defective genes can be omitted in workers and queens.

the queen may be inseminated by more than 15–20 males, it's polygynous, versus mono androus (andros being male in greek).

Some queens can mate with different species of ant and hybridize.

A nuptial flight of 10 queens in the first year and 1000 queens in the 10th year, all those individuals will have different genetics, because they all come from different fertilized eggs. The males are drones and all the same.

It can vary by species of ant, the queens can be all the same: in the ant Cataglyphis cursor, the queens are produced by parthenogenesis but workers arise from fertilized eggs, suggesting that genetic variation is vital for the worker caste (Pearcy et al. 2004).

Here is an attempt to unify the literature on ant caste development and evolution with a single theoretical framework, drawing on recent advances in evolutionary developmental biology.

They say that ant populations contain a balance little to big ants, a range of sizes, whereby queen like features, ovaries, wings and light receptors between teh eyes called ocelli, appear in steps as the larvae grow. Ants molt and the develop from small workers to large queens progressively.

If you check an soldier ant, she has a large head, it's almost as big as a queen's, although the body stays small. in the next stage of caste size, the body grows into nearly a queen, else with wings too.

If there is a lack of one caste, more of a particular kind are replenished.

To read the paper faster, search for keywords, for example hormones, they say:

Two endocrine hormones, juvenile hormone (JH) and ecdysone, are important regulators of developmental timing in insects. Pupation (and the cessation of larval growth) is triggered by ecdysone, and the action of ecdysone is inhibited by JH (Hiruma and Kaneko, 2013). Thus, treatment of larvae with JH or JH analogs leads to prolonged growth and larger size, as long as necessary nutrition is present. JH removal and/or ecdysone treatment leads to premature pupation and smaller adult size (Hiruma and Kaneko, 2013). This endocrine regulation of insect size has been demonstrated in Coleoptera and Lepidoptera, and is also supported by experiments in ants.

Some of the small ants have the potential to become queens, and when there is lots of food, more of the small ones will grow and make many queens that can fly on a hot day.

In M. rubra, larvae do not have the potential for queen development under normal conditions (Brian, 1979). However, larvae that are forced to diapause just before pupation reorganize their endocrine organs and delay pupation after growth is resumed (Brian, 1979). If sufficient nutrition is available, these totipotent larvae attain a large size and develop into queens

You may laugh by reading the effective genetic ant population mathematics at the end of the first citation. it is completely professor level, with a maths formula, which demonstrates that it's extraordinarily complex and variable effective genetic population distribution and gene expression.

If someone can say more about eusocial gene determination it's quite a difficult topic.

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  • $\begingroup$ I would be curious why someone downvoted this?! $\endgroup$ – Zaibis Oct 20 '17 at 5:51

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