Mitochondrial control region I and microsatellite analyses of endangered Philippine hornbill species (Aves; Bucerotidae) detect gene flow between island populations and genetic diversity loss.
BACKGROUND
The Visayan Tarictic Hornbill (Penelopides panini) and the Walden's Hornbill (Aceros waldeni) are two threatened hornbill species endemic to the western islands of the Visayas that constitute - between Luzon and Mindanao - the central island group of the Philippine archipelago. In order to evaluate their genetic diversity and to support efforts towards their conservation, we analyzed genetic variation in ~ 600 base pairs (bp) of the mitochondrial control region I and at 12-19 nuclear microsatellite loci. The sampling covered extant populations, still occurring only on two islands (P. panini: Panay and Negros, A. waldeni: only Panay), and it was augmented with museum specimens of extinct populations from neighboring islands. For comparison, their less endangered (= more abundant) sister taxa, the Luzon Tarictic Hornbill (P. manillae) from the Luzon and Polillo Islands and the Writhed Hornbill (A. leucocephalus) from Mindanao Island, were also included in the study. We reconstructed the population history of the two Penelopides species and assessed the genetic population structure of the remaining wild populations in all four species.


RESULTS
Mitochondrial and nuclear data concordantly show a clear genetic separation according to the island of origin in both Penelopides species, but also unravel sporadic over-water movements between islands. We found evidence that deforestation in the last century influenced these migratory events. Both classes of markers and the comparison to museum specimens reveal a genetic diversity loss in both Visayan hornbill species, P. panini and A. waldeni, as compared to their more abundant relatives. This might have been caused by local extinction of genetically differentiated populations together with the dramatic decline in the abundance of the extant populations.


CONCLUSIONS
We demonstrated a loss in genetic diversity of P. panini and A. waldeni as compared to their sister taxa P. manillae and A. leucocephalus. Because of the low potential for gene flow and population exchange across islands, saving of the remaining birds of almost extinct local populations - be it in the wild or in captivity - is particularly important to preserve the species' genetic potential.
Institute for Biology and Biochemistry, Unit of Evolutionary Biology/Systematic Zoology, University of Potsdam, Karl-Liebknecht-Str. 24-25, Haus 26, 14476 Potsdam, Germany.
Svenja
S
Sammler
Valerio
V
Ketmaier
Katja
K
Havenstein
Ulrike
U
Krause
Eberhard
E
Curio
Ralph
R
Tiedemann
D000818:Animals; D001717:Birds / Q000145:classification / Q000235:genetics*; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D056727:Endangered Species; D019143:Evolution, Molecular; D051456:Gene Flow; D005787:Gene Frequency; D014644:Genetic Variation; D005843:Geography; D006239:Haplotypes; D018895:Microsatellite Repeats / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010679:Philippines; D010802:Phylogeny; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial