Co-evolution: How does the need to sync development affect a system’s complexity?

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Alongside mapping the squid genome, researchers have been able to study the symbiotic evolution of a squid (Hawaiian bobtail) with a bacterium (Vibrio fischeri) that lives in the squid’s ink sac and helps camouflage it by emitting light in sync with the moon:

“It is basically acting like a little invisibility cloak for the squid,” said Jamie Foster, a microbiologist at the Space Life Sciences Lab at the University of Florida. In return for help with camouflage that protects against predators, the squid offers up sugars to feed the bacteria and lure them into the organ … Now, Foster and an international team of researchers have mapped the genome of a Hawaiian bobtail squid, creating a new tool to explore these questions. By parsing the squid’s genome, the team has already discovered that the evolution of its light organ followed a completely different pathway than that of a second symbiotic organ, which supports reproduction.Laura Poppick, “New Squid Genome Shines Light on Symbiotic Evolution” at Quanta

Paper. (open access)

Significance: Animal–microbe associations are critical drivers of evolutionary innovation, yet the origin of specialized symbiotic organs remains largely unexplored. We analyzed the genome of Euprymna scolopes, a model cephalopod, and observed large-scale genomic reorganizations compared with the ancestral bilaterian genome. We report distinct evolutionary signatures within the two symbiotic organs of E. scolopes, the light organ (LO) and the accessory nidamental gland (ANG). The LO evolved through subfunctionalization of genes expressed in the eye, indicating a deep evolutionary link between these organs. Alternatively, the ANG was enriched in novel, species-specific orphan genes suggesting these two tissues originated via different evolutionary strategies. These analyses represent the first genomic insights into the evolution of multiple symbiotic organs within a single animal host. – Mahdi Belcaid et al., Symbiotic organs shaped by distinct modes of genome evolution in cephalopods, PNAS February 19, 2019 116 (8) 3030-3035; published ahead of print February 19, 2019
Paper https://doi.org/10.1073/pnas.1817322116

We are told that little is known about co-evolution and symbiosis, which prompts a question: How does the requirement for synchronization affect the overall complexity of the system?

One reason that co-operative strategies are comparatively little studied has been the Darwinian focus on outright competition, which may be less common than we think.

See also: Plants have developed complex strategies to get ants to help them

Acacia Ants And Acacia Trees: An Irreducibly Complex Symbiotic Relationship?

Symbiosis Found In Cambrian Fossil Worms

and

Life continues to ignore what evolution experts say

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Comments

Our findings suggest that the two symbiotic organs within E. scolopes originated by different evolutionary mechanisms. Together, these analyses provide evidence for different patterns of genomic evolution of symbiotic organs within a single host. Our sequencing efforts have resulted in the most comprehensive cephalopod genome assembly to date, revealing the expansive and highly repetitive nature of the E. scolopes genome. large intergenic distances may be responsible for the evolution of unique regulatory mechanisms. Our analyses of the Hawaiian bobtail squid genome revealed large-scale genome reorganization, which preceded the coleoid cephalopod radiation, and provide evidence for two different patterns of genomic evolution that contributed to functional novelty. First, the extensive structural reorganization through the loss of ancient bilaterian microsynteny and increase in genome size through repetitive element expansions resulted in a unique genomic architecture that may have contributed to the innovations in the general cephalopod body plan. Second, the coding and surrounding regulatory regions of microbe-associated tissues suggest distinctive evolutionary patterns, such as the expansion of genes associated with immunity and light production in the LO. In the ANG, the prevalence of taxon-specific, or orphan, gene expression suggests a highly derived organ that evolved by a different means than the LO, perhaps due to unique selection pressures. Overall, our results set the stage for further functional analysis of genomic innovations that led to the evolution of symbiotic organs in a morphologically and behaviorally complex clade.
Ok, and...?PeterA_{February 22, 2019
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There’s little “evo” (just adaptation) in “evo-devo”, but no serious macroevo. Evo-devo is mostly devo.PeterA_{February 20, 2019
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