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...including the description by Mérot et al. of the new timareta
from Peru, <i>thelxinoe</i>!<br>
<br>
Supple MA, Hines HM, Dasmahapatra KK, Nielsen DM, Lavoie C, Ray DA,
Salazar C, McMillan WO, Counterman BA. 2013. Genomic architecture of
adaptive color pattern divergence and convergence in Heliconius
butterflies. Genome Research (online pre-publication)<br>
<br>
Identifying the genetic changes responsible for adaptive variation
in natural populations is keyto understanding how biodiversity is
generated. The mosaic of mimetic wing patterns inHeliconius
butterflies makes them an excellent system for exploring the origins
of adaptive variation using next-generation sequencing techniques.
In this study, we use RNA-Seq toannotate the genomic interval
modulating red color pattern variation and whole genomeresequencing
of multiple color morphs to identify a narrow region responsible for
adaptivedivergence and convergence in Heliconius wing patterns.
Using population and phylogeneticanalyses across four hybrid zones
between color morphs of H. erato and two hybrid zones ofthe co-mimic
H. melpomene, we identify a shared 65 kb island of divergence in the
intergenicregion near optix, the gene which was previously shown to
be responsible for the complex redpattern variation in Heliconius.
Our dense SNP analysis reveals several sites in this region
perfectly associated with red color pattern phenotype in both
species. This region likely contains multiple cis-regulatory
elements that control discrete expression domains of optix.The
parallel signatures of genetic differentiation in H. erato and H.
melpomene support ashared regulatory architecture between the two
distantly related co-mimics; however,phylogenetic analyses and the
absence of shared candidate SNPs suggest mimetic patterns ineach
species evolved independently. Using a combination of
next-generation sequencingtechniques, we have refined our
understanding of the genetic architecture of wing patternvariation
in Heliconius and gained important insights into the evolution of
novel adaptivephenotypes in natural populations.<br>
<br>
<br>
Mérot C, Mavárez J, Evin A, Dasmahapatra KK, Mallet J, Lamas G,
Joron M. 2013. Genetic differentiation without mimicry shift in a
pair of hybridizing Heliconius species (Lepidoptera: Nymphalidae).
Biological Journal of the Linnean Society (online early).<br>
<br>
Abstract: Mimetic butterflies in the genus Heliconius have undergone
rapid adaptive radiation for warning patterns, and are excellent
models to study the mechanisms underlying diversification. In
Heliconius, mimicry rings typically involve distantly-related
species, while closely related species often join different mimicry
rings. Genetic and behavioural studies have shown how a reduction of
gene flow in Heliconius is often mediated, in part, by natural and
sexual selection on wing colour pattern. However, recent studies
have uncovered new cases in which pairs of closely-related species
are near-perfect mimics of each other. Here, we provide
morphometrical and genetic evidence for the coexistence of two very
closely related, hybridizing co-mimics on the eastern Andean
foothills, H. melpomene amaryllis and H. timareta ssp. nov., which
is described here as <b>H. t. thelxinoe</b>. A joint analysis of
multilocus genotyping and geometric morphometrics of wing shape
shows a high level of differentiation between the two species with
only limited gene flow and mixing. Some degree of mixing can be
detected, although putative hybrids were rare (one out of 175
specimens was a clear hybrid). In contrast, we found phenotypic
differentiation between populations of H. timareta thelxinoe,
possibly indicative of strong selection for local mimicry in
different communities. In this pair of species where promiscuous
exchange of wing patterning alleles has been demonstrated, the
absence of breakdown of genetic isolation when wing pattern are
similar implies that factors other than wing patterns keep the two
taxa separate, such as chemical or behavioural signals, or
ecological adaptation along a strong altitudinal gradient.<br>
<br>
<br>
Cardoso MZ, Gilbert LE. 2013. Pollen feeding, resource allocation
and the evolution of chemical defence in passion vine butterflies.
Journal of Evolutionary Biology (online early).<br>
<br>
Abstract: Evolution of pollen feeding in Heliconius has allowed
exploitation of rich amino acid sources and dramatically reorganized
life-history traits. In Heliconius, eggs are produced mainly from
adult-acquired resources, leaving somatic development and
maintenance to larva effort. This innovation may also have spurred
evolution of chemical defence via amino acid-derived cyanogenic
glycosides. In contrast, nonpollen-feeding heliconiines must rely
almost exclusively on larval-acquired resources for both
reproduction and defence. We tested whether adult amino acid intake
has an immediate influence on cyanogenesis in Heliconius. Because
Heliconius are more distasteful to bird predators than close
relatives that do not utilize pollen, we also compared cyanogenesis
due to larval input across Heliconius species and nonpollen-feeding
relatives. Except for one species, we found that varying the amino
acid diet of an adult Heliconius has negligible effect on its
cyanide concentration. Adults denied amino acids showed no decrease
in cyanide and no adults showed cyanide increase when fed amino
acids. Yet, pollen-feeding butterflies were capable of producing
more defence than nonpollen-feeding relatives and differences were
detectable in freshly emerged adults, before input of adult
resources. Our data points to a larger role of larval input in adult
chemical defence. This coupled with the compartmentalization of
adult nutrition to reproduction and longevity suggests that one
evolutionary consequence of pollen feeding, shifting the burden of
reproduction to adults, is to allow the evolution of greater
allocation of host plant amino acids to defensive compounds by
larvae<br>
<br>
Hill RI, Gilbert LE, Kronforst MR. 2013. Cryptic genetic and wing
pattern diversity in a mimetic Heliconius butterfly. Molecular
Ecology (online early).<br>
<br>
Abstract: Despite rampant colour pattern diversity in South America,
Heliconius erato exhibits a "postman" wing pattern throughout most
of Central America. We examined genetic variation across the range
of H. erato, including dense sampling in Central America, and
discovered a deep genetic break, centred on the mountain range that
runs through Costa Rica. This break is characterized by a novel
mitochondrial lineage, which is nearly fixed in northern Central
America, that branches basal to all previously described
mitochondrial diversity in the species. Strong genetic
differentiation also appears in Z-linked and autosomal markers, and
it is further associated with a distinct, but subtle, shift in wing
pattern phenotype. Comparison of clines in wing phenotype, mtDNA and
nuclear markers indicate they are all centred on the mountains
dividing Costa Rica, but that cline width differs among data sets.
Phylogeographical analyses, accounting for this new diversity,
rewrite our understanding of mimicry evolution in this system. For
instance, these results suggest that H. erato originated west of the
Andes, perhaps in Central America, and as many as 1 million years
before its co-mimic, H. melpomene. Overall our data indicate that
neutral genetic markers and colour pattern loci are congruent and
converge on the same hypothesis. H. erato originated in northwest
South America or Central America with a "postman" phenotype and then
radiated into the wealth of colour patterns present today<br>
<pre class="moz-signature" cols="72">--
James Mallet
OEB & GEE Depts
Harvard University & University College London
Cambridge, MA 02138 and LONDON WC1E 6BT
USA tel: +(1)617-496-5350
<a class="moz-txt-link-abbreviated" href="http://www.ucl.ac.uk/taxome/jim">www.ucl.ac.uk/taxome/jim</a></pre>
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