Hemignathus

About: Hemignathus is a research topic. Over the lifetime, 9 publications have been published within this topic receiving 217 citations.

Adaptive Radiation Genomics of Two Ecologically Divergent Hawai'ian Honeycreepers: The 'akiapōlā'au and the Hawai'i 'Amakihi

Abstract: The Hawai'ian honeycreepers (drepanids) are a classic example of adaptive radiation: they adapted to a variety of novel dietary niches, evolving a wide range of bill morphologies. Here we investigated genomic diversity, demographic history, and genes involved in bill morphology phenotypes in 2 honeycreepers: the 'akiapōlā'au (Hemignathus wilsoni) and the Hawai'i 'amakihi (Chlorodrepanis virens). The 'akiapōlā'au is an endangered island endemic, filling the "woodpecker" niche by using a unique bill morphology, while the Hawai'i 'amakihi is a dietary generalist common on the islands of Hawai'i and Maui. We de novo sequenced the 'akiapōlā'au genome and compared it to the previously sequenced 'amakihi genome. The 'akiapōlā'au is far less heterozygous and has a smaller effective population size than the 'amakihi, which matches expectations due to its smaller census population and restricted ecological niche. Our investigation revealed genomic islands of divergence, which may be involved in the honeycreeper radiation. Within these islands of divergence, we identified candidate genes (including DLK1, FOXB1, KIF6, MAML3, PHF20, RBP1, and TIMM17A) that may play a role in honeycreeper adaptations. The gene DLK1, previously shown to influence Darwin's finch bill size, may be related to honeycreeper bill morphology evolution, while the functions of the other candidates remain unknown.

Multiple Reversals of Bill Length over 1.7 Million Years in a Hawaiian Bird Lineage

Abstract: Evolutionary change has been documented over geological time, but reversals in morphology, from an ancestral state to a derived state and back again, tend to be rare. Multiple reversals along the same lineage are even rarer. We use the chronology of the Hawaiian Islands and an avian example, the Hawaiian honeycreeper ‘amakihi (Hemignathus spp.) lineage, which originated on the oldest main island of Kaua‘i 1.7 million years ago, to examine the process of sequential reversals in bill length. We document three single and two multiple reversals of bill length on six main islands from oldest to youngest, consistent with the phylogeny of the lineage. Longer bills occur on islands with endemic species, including phylogenetically relevant outgroups, that may compete with or dominate the ‘amakihi. On islands without those species, the ‘amakihi had shorter bills of similar length. Both types of reversals in morphology in this lineage integrate microevolutionary processes with macroevolution in the adaptive ...

A specimen of Nuku pu'u (Aves: Drepanidini: Hemignathus lucidus) from the island of Hawai'i

Abstract: A specimen of Nuku pu'u (Hemignathus lucidus Lichtenstein), collected by the U.S. Exploring Expedition in 1840 or 1841, is shown to have come from the island of Hawai'i. This is the first specimen evidence of the spe­ cies for that island and the first evidence of probable sympatry of H. lucidus with the 'Akia p6la'au (H. wilsoni Rothschild). Skull morphology provides ad­ ditional evidence that these two species do not constitute a superspecies. dible is curved in the same arc as the pre­ maxilla, and the 'Akia p6Ia'au, H. wilsoni Rothschild, 1893, in which the mandible is straight and more robust. Currently, H. lucidus is considered to have occurred in historic times only on the islands of Kaua'i (H. l. hanapepe), O'ahu (H. l. luci­ dus), and Maui (H. l. affinis), whereas H. wilsoni is endemic to the island of Hawai'i (Figure 1). This apparently allopatric dis­ tribution has caused some authors to regard H. lucidus and H. wilsoni as forming a "superspecies" (e.g., Amadon 1950: 169). Herein we document specimen evidence of the historical occurrence of H. lucidus on Hawai'i, where it would presumably have OF THE BIRDS THAT make up the remarkable adaptive radiation of Hawaiian finches (Carduelinae: Drepanidini), few are as dis­ tinctive as the "heterobills" of the genus Hemignathus. (The history of the taxa that have been included under the name Hemi­ gnathus involves some of the most complex nomenclatural problems in Hawaiian orni­ thology. Here we use Hemignathus in the sense of Amadon (1950), and of most pre­ vious authors, to include the "heterobills" H. lucidus and H. wilsoni, and the 'akialoas (Hemignathus obscurus group). We entertain reservations that even this assemblage is monophyletic, and we manifestly disagree (Olson and James 1988) with the inclusion (American Ornithologists' Union 1983) of the 'amakihis (Loxops virens and relatives of Amadon (1950)) in Hemignathus, following Pratt (1979). If that course is followed, how­ ever, the 'Akia p61a'au must be known as H. munroi, rather than H. wilsoni, the name we use here.) In the "heterobills" the strongly curved upper portion of the bill (premaxilla) greatly exceeds the mandible in length, thus giving rise to the unique "half-billed" ap­ pearance, whence the name Hemignathus. Two species of these "heterobills" are now recognized, the Nuku pu'u, Hemignathus lu­ cidus Lichtenstein, 1839, in which the man-