地球上の脊椎動物種は従来推定の2倍の可能性(Study finds Earth may have twice as many vertebrate species as previously thought)

2026-03-02 アリゾナ大学

米国アリゾナ大学の研究チームは、地球上の脊椎動物の種数が従来の推定より少なくとも2倍存在する可能性があると報告した。従来の分類は外形的特徴に基づいていたが、遺伝子解析が進んだことで、多くの「隠れた種(cryptic species)」が見逃されてきたことがわかった。これらは外見はほぼ同じでも、DNAレベルでは独立した進化系統を持つ種であり、形態的分類では同一種と見なされていたが、分子データでは別個の種として区別できる。魚類、鳥類、哺乳類、両生類、爬虫類など主要なグループで、形態に基づく1種につき平均2つの隠れた種が潜んでいるという傾向が観察され、地球の脊椎動物種多様性は大幅に過小評価されている可能性が示唆された。この発見は生物多様性評価や保全戦略に大きな影響を与えるとされる。

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隠蔽種は脊椎動物全体に広く分布している Cryptic species are widespread across vertebrates

Yinpeng Zhang;John J. Wiens
Proceedings of the Royal Society B  Published:04 Feb 2026
DOI:https://doi.org/10.1098/rspb.2025.2377

地球上の脊椎動物種は従来推定の2倍の可能性(Study finds Earth may have twice as many vertebrate species as previously thought)

Abstract

Many species delimited by morphological data contain two or more species that are distinct based on molecular data (i.e. cryptic species). Cryptic species have important implications for ecology, evolution and conservation. For example, morphology-based species of limited conservation concern can contain cryptic species that are in imminent danger of extinction. Here, we examined the prevalence of cryptic species across vertebrates. We also examined the controversial use of mitochondrial data, and whether they overestimate or underestimate cryptic species relative to nuclear data. We obtained usable estimates of species limits from 373 studies. We found that each morphology-based species contained approximately two cryptic species on average. This number was surprisingly similar across major groups despite dramatic differences in ecology and physiology (fishes versus birds), and similar to comparable estimates in insects. Cryptic species numbers from mitochondrial data alone were often higher than from nuclear data, but were generally not statistically different. Overall, our results show that cryptic species are numerous and widespread across vertebrates. These results suggest that cryptic species should not be ignored in analyses of species richness, speciation and extinction in living and fossil organisms. Furthermore, testing for cryptic species across morphology-based vertebrate species should be an urgent priority for conservation.

1903自然環境保全
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