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Taxa relegated to synonymy with other superficially similar taxa based on herbarium-based taxonomy may be distinct species that are only ‘rediscovered’ on the collection of new, multi-disciplinary evidence. Here we investigate the case of Satyrium jacottetiae that has been included in the concept of S. membranaceum (Orchidaceae). The two taxa share similarities in some conspicuous traits, such as the dry and membranous floral bracts, light pink labellum and laceration of the petals, but a quantitative morphometric analysis based on 23 floral traits showed that the two taxa differentiate in ordination space. We found that the taxa can be distinguished by features of the rostellum (short and broad in S. jacottetiae and elongate and notched in S. membranaceum), which are not readily apparent from examination of herbarium specimens. A phylogenetic analysis of nuclear ribosomal DNA sequences further revealed that accessions of S. jacottetiae belong to a clade that contains two other Satyrium spp. but not S. membranaceum. The two taxa have largely non-overlapping distributions on slightly different soil types, but they also maintain their integrity in the few zones of overlap despite evidence indicating that both are primarily pollinated by nocturnal moths. Coexistence in these cases of sympatry appears to be facilitated by a sequential difference in flowering times. We conclude that S. jacottetiae and S. membranaceum are morphologically, phylogenetically, geographically and ecologically distinct and should therefore be recognized as separate species. This study highlights the importance of multi-disciplinary taxonomic effort to avoid under-assessment of biodiversity.

The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs.

Bees are frequent visitors to plants that, on the basis of floral traits, would be expected to be specialized for bird pollination. We conducted bird exclusion experiments to establish the contribution that bees make to the female component of pollination success of five “ornithophilous” Aloe species in the succulent‐rich subtropical thicket vegetation in southeastern South Africa. Experiments showed that all five aloes are genetically self‐incompatible and require cross‐pollination for seed set. Seed set in flowers exposed to both bird and bee visitors was generally severalfold higher than in flowers exposed to bee visitors only. The magnitude of this effect varied greatly among species and was affected by floral traits and bee behavior. In three aloes where the relatively short corolla tubes are blocked by exserted filaments, bees made a negligible contribution to seed production. However, in two aloes with long tubular flowers and included filaments, bees often crawled into the perianth tube to obtain ...

Coexistence among species that lack genetic barriers to hybridization usually depends on pre-mating isolating barriers. It has been difficult to explain coexistence among African Aloe species because they readily hybridize, often flower simultaneously and are mostly bird-pollinated. Here we show that co-flowering aloes in a succulent thicket community in South Africa partition the fauna of flower-visiting birds. Aloe species with small amounts of concentrated nectar in long corolla tubes were pollinated primarily by long-billed sunbirds. These species co-flowered with species with large amounts of dilute nectar in short corolla tubes which were pollinated primarily by short-billed, generalist nectarivores. Aloe species which share pollinators tend to have divergent flowering times and differences in pollen placement on birds. Without these isolating barriers, genetic dissolution of sympatric Aloe species would be likely.