Ecological comparison and Molecular Phylogeny of Japanese Pygmy Woodpecker Populations

了解鸟类群落起源的方法之一是探索每个物种在当地种群的建立历史。种距法则是一种重要的地理学法则，也是种面积法则，通常指离源越近的岛屿，其种数越多，定殖率越高。然而，有几个岛屿没有日本侏儒啄木鸟（JPW，Picoides kizuki）靠近日本主岛，尽管有足够好的森林栖息地。JPW是日本列岛和各种森林中的常见物种，包括城市周围的小森林岛屿。这一事实表明，有一些因素限制了一个物种在较近的栖息地岛屿上的定居。捕食者可能是其中之一，但JPW不是，因为该物种在20世纪80年代将其分布范围扩大到城市地区，当时丛林乌鸦和棕耳白头翁等捕食者的数量也增加了它们的数量。这片森林在这个时代已经支离破碎，与世隔绝。我认为较长的距离可能使JPW在城市公园定居，或者在遥远的森林岛屿上短期灭绝率较低。同样的机制本可以在联合PW的地理位置上发挥作用。我一直在重新确认JPW的分布模式，并比较了几个JPW种群的翅膀形状。机翼在冲绳和奄美群岛，南部和偏远的岛屿，表明他们的飞行能力较低。不过，在中距离的三宅岛上，比在源大陆上要尖锐一些。在主岛和这些岛屿之间有几个JPW缺乏岛屿。这些事实似乎支持这一假设。

One of the ways to understand the origin of the avian community, is to explore the history of establishment of the local populations of each species. Species-distance rule, an important biogeographic rule as well as that of species-area, usually says more species or higher colonization rate on the closer island to the source. However, there are several islands without the Japanese Pygmy Woodpecker (JPW, Picoides kizuki) close to Japanese Main islands, in spite of that there is good enough forest habitat. JPW is a common species in Japanese archipelago and in a wide variety of forests, including small forest islands around the cities. This fact suggests there are some factors which limit a species colonization on the closer habitat island. Predators can be one of them, but not for JPW, because the species expanded its distribution in 1980's into urban area, where the number of predators such as Jungle Crow and Brown-eared Bulbul also increased their population there at that time. The forest had been fragmented and isolated in this era. I think the longer distance might made JPW to colonize at the city parks or short time extinction rate is lower on the distant forest islands. The same mechanism could have been worked in the geographic situation of JPW. I have been reconfirming the distribution pattern of JPW and compared the wing shape of several JPW populations. The wing was pointed less on Okinawa and Amami Islands, southern and remote islands, suggesting their lower flight ability. However it was sharper on Miyake island of middle distance than it was in the source mainland. There are several JPW lacking islands between main land and those islands. These facts seem to support the hypothesis.