IUBio

Poecilogony

Geoff Read g.read at niwa.cri.nz
Wed Jul 21 21:18:50 EST 1999


> I was wondering if anyone had any neat examples of poecilogony that 
> they could put me on to.  Professor Jamieson recalls one example in 
> Streblospio benedicti but we can't find the reference for it. 

As mentioned this was probably one of Lisa Levin's. Some of the many S. 
benedicti papers of hers, with Stanley Rice & other associates are listed in: 
 
Rice, S. A., & L. A. Levin. 1998. Streblospio gynobranchiata, a new 
spionid polychaete species (Annelida: Polychaeta) from Florida and the 
Gulf of Mexico with an analysis of phylogenetic relationships within the 
genus Streblospio.— Proceedings of the Biological Society of Washington, 
111:694-707.

The review paper of Hoagland and Robertson should be mentioned. I think 
we can safely say now they were overly sceptical (and there is a bizarre 
misinterpretation of a certain person's 1975 Polydora paper on p116 :-)).  

Hoagland, K. E., & R. Robertson. 1988. An assessment of poecilogony in 
marine invertebrates: phenomenon or fantasy?— Biological Bulletin, 
174:95-108.

Another review:

Chia, F. S., G. Gibson, & P. Y. Qian. 1996. Poecilogony As A 
Reproductive Strategy Of Marine Invertebrates.— Oceanologica Acta, 
19:203-208.

I am looking forward to reading this next paper, and I give the abstract in 
full since it is quite recent.

Morgan, T. S., A. D. Rogers, G. L. J. Paterson, L. E. Hawkins, & M. 
Sheader. 1999. Evidence for poecilogony in Pygospio elegans 
(Polychaeta : Spionidae).— Marine Ecology   Progress Series, 178:121-
132.

ABSTRACT:
The spionid polychaete Pygospio elegans displays more than one 
developmental mode. Larvae may develop directly, ingesting nurse eggs 
while brooded in capsules within the parental tube, or they may hatch early 
to feed in the plankton before settling. Asexual reproduction by architomic 
fragmentation also occurs. Geographically separated populations of P, 
elegans often display different life histories. Such a variable life history 
within a single species may be interpreted either as evidence of sibling 
speciation or of reproductive flexibility (poecilogony). Four populations 
from the English Channel were found to demonstrate differing Life histories 
and were examined for morphological and genetic variability to determine 
whether P, elegans is in fact a cryptic species complex. Significant but 
minor inter-population polymorphisms were found in the distribution of 
branchiae and the extent of spoonlike hooded hooks. These externally 
polymorphic characters did not vary with relation to life history, and 
variation fell within the reported range for this species. Cellulose acetate 
electrophoresis was used to examine 10 allozyme loci, 5 of which were 
polymorphic. Overall, observed heterozygosity (H-o = 0.161) was lower 
than that expected under Hardy-Weinberg equilibrium (H-e = 0.228). 
Significant heterozygote deficiencies, detected at the Est* and Xdh* loci in 
all populations (except Xdh* at Ryde Sand, Isle of Wight, UK), are 
discussed. F-statistics were used to examine patterns of genetic structuring 
among both separate and pooled populations. F-ST values at all 
polymorphic loci indicated a significant level of genetic differentiation 
between populations, most probably related to isolation by geographic 
distance. No direct relationship between life history and genetic structure 
could be detected. Overall genetic identity among the 4 populations was 
high (I= 0.977 to 0.992). Overall, populations displaying larval brooding did 
not appear to be reproductively isolated from populations displaying a fully 
planktonic larval mode. Present data support the hypothesis that P. Elegans 
is poecilogonous.

--
  Geoff Read <g.read at niwa.cri.nz>

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