[Coral-List] Publication: Indo-Pacific gorgonian Isis hippuris: genetic fixation or phenotypic plasticity?

[Sonia Rowley]

Dear List

Please find a link below to a new paper on the: "Environmental influences
on the Indo–Pacific octocoral Isis hippuris Linnaeus 1758 (Alcyonacea:
Isididae): genetic fixation or phenotypic plasticity?"

https://peerj.com/articles/1128.pdf

*Abstract:*

As conspicuous modular components of benthic marine habitats, gorgonian
(sea fan) octocorals have perplexed taxonomists for centuries through their
shear diversity, particularly throughout the Indo–Pacific. Phenotypic
incongruence within and between seemingly unitary lineages across
contrasting environments can provide the raw material to investigate
processes of disruptive selection. Two distinct phenotypes of the Isidid Isis
hippuris Linnaeus, 1758 partition between differing reef environments:
long-branched bushy colonies on degraded reefs, and short-branched
multi/planar colonies on healthy reefs within the Wakatobi Marine National Park
(WMNP), Indonesia. Multivariate analyses reveal phenotypic traits between
morphotypes were likely integrated primarily at the colony level with
increased polyp density and consistently smaller sclerite dimensions at the
degraded site. Sediment load and turbidity, hence light availability,
primarily influenced phenotypic differences between the two sites. This
distinct morphological dissimilarity between the two sites is a reliable
indicator of reef health; selection primarily acting on colony morphology,
porosity through branching structure, as well as sclerite diversity and
size. ITS2 sequence and predicted RNA secondary structure further revealed
intraspecific variation between I. hippuris morphotypes relative to such
environments (ΦST = 0.7683,P < 0.001). This evidence suggests—but does not
confirm—that I. hippuris morphotypes within the WMNP are two separate
species; however, to what extent and taxonomic assignment requires further
investigation across its full geographic distribution. Incongruence between
colonies present in the WMNP with tenuously described Isis alternatives (Isis
reticulata Nutting, 1910, Isis minorbrachyblasta Zou, Huang & Wang, 1991),
questions the validity of such assignments. Furthermore, phylogenetic
analyses confirm early taxonomic suggestion that the characteristic jointed
axis of the Isididae is in fact a convergent trait. Thus the polyphyletic
nature of the Isididae lies in its type species I. hippuris, being
unrelated to the rest of its family members.

-- 
Sonia J. Rowley PhD
Postdoctoral Research Associate
University of Hawai'i at Manoa
POST 713, 1680 East-West Road
Honolulu, HI 96822
+1 808 348 6224

Research Affiliate
Bernice Pauahi Bishop Museum
1525 Bernice St, Honolulu,
HI 96817, USA