We compare the historical demographies of two Mü llerian comimetic butterfly species: Heliconius erato and Heliconius melpomene. These species show an extensive parallel geographic divergence in their aposematic wing phenotypes. Recent studies suggest that this coincident mosaic results from simultaneous demographic processes shaped by extrinsic forces over Pleistocene climate fluctuations. However, DNA sequence variation at two rapidly evolving unlinked nuclear loci, Mannose phosphate isomerase (Mpi) and Triose phosphate isomerase (Tpi), show that the comimetic species have quite different quaternary demographies. In H. erato, despite ongoing lineage sorting across the Andes, nuclear genealogical estimates showed little geographical structure, suggesting high historical gene flow. Coalescent-based demographic analysis revealed population growth since the Pliocene period. Although these patterns suggest vicariant population subdivision associated with the Andean orogeny, they are not consistent with hypotheses of Pleistocene population fragmentation facilitating allopatric wing phenotype radiation in H. erato. In contrast, nuclear genetic diversity, , in H. melpomene was reduced relative to its comimic and revealed three phylogeographical clades. The pattern of coalescent events within regional clades was most consistent with population growth in relatively isolated populations after a recent period of restricted population size. These different demographic histories suggest that the wingpattern radiations were not coincident in the two species. Instead, larger effective population size (Ne) in H. erato, together with profound population change in H. melpomene, supports an earlier hypothesis that H. erato diversified first as the model species of this remarkable mimetic association.

We report a dense genetic linkage map of Heliconius erato, a neotropical butterfly that has undergone a remarkable adaptive radiation in warningly colored mimetic wing patterns. Our study exploited natural variation segregating in a cross between H. erato etylus and H. himera to localize wing color pattern loci on a dense linkage map containing amplified fragment length polymorphisms (AFLP), microsatellites, and single-copy nuclear loci. We unambiguously identified all 20 autosomal linkage groups and the sex chromosome (Z). The map spanned a total of 1430 Haldane cM and linkage groups varied in size from 26.3 to 97.8 cM. The average distance between markers was 5.1 cM. Within this framework, we localized two major color pattern loci to narrow regions of the genome. The first gene, D, responsible for red/ orange elements, had a most likely placement in a 6.7-cM region flanked by two AFLP markers on the end of a large 87.5-cM linkage group. The second locus, Sd, affects the melanic pattern on the forewing and was found within a 6.3-cM interval between flanking AFLP loci. This study complements recent linkage analysis of H. erato's comimic, H. melpomene, and forms the basis for marker-assisted physical mapping and for studies into the comparative genetic architecture of wing-pattern mimicry in Heliconius.

Tropical orchids constitute the greater part of orchid diversity, but little is known about their obligate mycorrhizal relationships. The specificity of these interactions and associated fungal distributions could influence orchid distributions and diversity. We investigated the mycorrhizal specificity of the tropical epiphytic orchid Ionopsis utricularioides across an extensive geographical range. DNA ITS sequence variation was surveyed in both plants and mycorrhizal fungi. Phylogeographic relationships were estimated for the mycorrhizal fungi. Orchid functional outcomes were determined through in vitro seed germination and seedling growth with a broad phylogenetic representation of fungi. Most fungal isolates derived from one clade of Ceratobasidium (anamorphs assignable to Ceratorhiza), with 78% within a narrower phylogenetic group, clade B. No correlation was found between the distributions of orchid and fungal genotypes. All fungal isolates significantly enhanced seed germination, while fungi in clade B significantly enhanced seedling growth. These results show that I. utricularioides associates with a phylogenetically narrow, effective fungal clade over a broad distribution. This preference for a widespread mycorrhizae may partly explain the ample distribution and abundance of I. utricularioides and contrasts with local mycorrhizal diversification seen in some nonphotosynthetic orchids. Enhanced orchid function with a particular fungal subclade suggests mycorrhizal specificity can increase orchid fitness.

We report the first genetic linkage map of Heliconius erato, a species that shows remarkable variation in its warningly colored wing patterns. We use crosses between H. erato and its sister species, H. himera, to place two major color pattern genes, D and Cr, on a linkage map containing AFLP, allozyme, microsatellite and single-copy nuclear loci. We identified all 21 linkage groups in an initial genetic screen of 22 progeny from an F1 female  male H. himera family. Of the 229 markers, 87 used to identify linkage groups were also informative in 35 progeny from a sibling backcross (H. himera female  F1 male). With these, and an additional 33 markers informative in the second family, we constructed recombinational maps for 19 of the 21 linkage groups. These maps varied in length from 18.1 to 431.1 centimorgans (cM) and yielded an estimated total length of 2400 cM. The average distance between markers was 23 cM, and eight of the 19 linkage groups, including the sex chromosome (Z) and the chromosome containing the Cr locus, contained two or more codominant anchor loci. Of the three potential candidate genes mapped here, Cubitus interruptus (Ci), Decapentaplegic (Dpp) and Wingless (Wg), only Ci was linked, although loosely, to a known Heliconius color pattern locus. This work is an important first step for constructing a denser genetic map of the H. erato color pattern radiation and for a comparative genomic study of the architecture of mimicry in Heliconius butterflies. Heredity (2005) 94, 408-417.

The Heliconius butterflies offer exceptional opportunities for the study of the ecology and evolution of mimicry. Despite previous reports of difficulties in the development of microsatellite loci in Lepidoptera, we characterize 15 polymorphic loci in H. erato that show promise for genetic mapping and population studies in this and other species. Levels of variation were high, in both numbers and size ranges of alleles. The loci showed broad amplification success across the genus and in two other genera. All loci that amplified in a population of H. melpomene were polymorphic.

The grasshopper Chorthippus parallelus is genetically differentiated over its range into at least five major geographical subdivisions. Two of these subdivisions, designated as subspecies, meet and form a hybrid zone in the Pyrenees. These subspecies differ for a wide range of morphological, behavioural and chromosomal characters, which vary clinally across the zone. A further geographical subdivision exists within Italy. Here we present the first evidence for chromosomal divergence between populations of the grasshopper north and south of the Alps. Across two Alpine cols (Col de Larche, between France and Italy; Passo de Resia, between Austria and Italy), these populations differ in both structural and functional components of the X‐chromosome. Northern Alpine individuals possess an active nucleolar organizing region (NOR) at the distal end of the X‐chromosome and an associated region of heterochromatin (C‐band). Both these features are absent from individuals from the south of the Alps. However, all individuals examined carry distally located rDNA on the X‐chromosome. Clinal transition was examined in the distal C‐band in transects through the two cols. The cline centres are roughly coincident with the tops of the cols. Both clines were of similar widths (Col de Larche, 21.88 km; Passo de Resia, 24.05 km), and therefore much wider than those for an X‐linked distal C‐band in the Pyrenean hybrid zone. This suggests that there are different selective pressures on the cytogenetic characters in the Alps. The results are discussed in the context of the historical population dynamics of the species in relation to the climatic changes associated with the Pleistocene ice ages.

As species are the common currency for conservation efforts, their accurate description is essential for efficient preservation of biological diversity. The genus Microtis (Orchidaceae) is typified by a paucity of consistent morphological characters, confounding taxonomic attempts. We report the results of a study of the conservation genetics of the recently discovered, endangered Australian orchid species M. angusii (Jones). This species was known only from one small population, with identification of further populations hampered by taxonomic difficulties. We used a combination of 122 AFLP markers and DNA sequence variation in the ribosomal ITS gene region to investigate the population genetic structure of the type population of M. angusii. Six further putative M. angusii populations were also analysed with these markers. Two of these populations showed high genetic affinity to M. angusii, bearing identical ITS sequences. Both the type and a second population were invariable across all AFLP loci. The third population, 3 km distant, showed minor genetic differentiation. These two new populations warrant immediate protection. Phylogenetic relationships between M. angusii and close relatives revealed its genetic affiliation to an unidentified, more distant population, and to the species M. unifolia. Given the propensity in Microtis for both selfing and clonality, mechanisms that both reduce within population variability and promote divergence between isolated populations, we recommend an extended study of both the genetic structure and breeding systems in the M. angusii/M. unifolia group, in order to ensure that the protection provided is both adequate and justified.

The natural vanilla essence is obtained principally from the fruits of the species Vanilla planifolia, a member of the Vanilla aromatic clade, and native to the neo-tropics. Colombia is an important center of diversity for the genus with 22 Vanilla species reported, of which 18 belong to the aromatic clade. Colombian native Vanilla species comprise important genetic resources for the vanilla crop. Although there is no tradition of cultivation of vanilla in the country, these species have potential for establishment in sustainable agroforestry systems. Nonetheless, Vanilla, like many orchid species, is subject to both intrinsic and extrinsic conservation threats. This article outlines an integrated strategy for conservation, incorporating in situ, ex situ and circa situm measures to ensure the conservation of Vanilla species in Colombia, and to promote their sustainable use in community-based cultivation programs. This proposed strategy is also relevant for conservation managers in other countries with native Vanilla species.