| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（口頭発表） J01-16 （Oral presentation）

#### Mechanisms of speciation vary with latitude【E】

*Jose Said GUTIERREZ-ORTEGA（RIKEN iTHEMS）

The latitudinal gradient of species diversity is the most conspicuous macroecological pattern, yet the dynamics that shape and maintain it remain largely unknown. Communities serve as the sources of new species, which in turn introduce innovations that promote novel interactions. Understanding the entanglement between latitude and the speciation process may clarify the link between micro- and macro-evolution. In this research, I analyzed phylogenetic, geographic, and climatic data for almost 4,000 species across eight groups of plants and vertebrates. Using niche models, I identified whether sister pairs have diverged via niche conservatism (NC), niche divergence (ND), or niche equivalency (NE). While NC and NE are typically observed in specialists, NE is characteristic of generalists. NC and ND occur more frequently in species pairs living in allopatry and sympatry, respectively. Using temperature seasonality as a main predictor, a Dirichlet regression shows that latitudinal bands near the equator exhibit the highest proportions of NC and NE. The proportions of these modes decrease as latitude increases, suggesting that tropical species tend to maintain their ancestral niches. The opposite pattern is observed in ND: species at high latitudes are more likely to shift their niches, suggesting that speciation at higher latitudes is driven by adaptation to harsh or seasonal environments. To explain this latitude-associated pattern, I constructed an agent-based model to simulate how lineages disperse across latitudes, with high latitudes representing harsher environments in terms of habitability and carrying capacity. The environment and the adaptability of species within a given latitudinal band provide a probability that a species will be categorized as NC, ND, or NE. The simulation outcomes were concordant with the empirical data, supporting the conclusion that the tropics represent a "niche conservation trap" for specialists, while lineages that successfully disperse to high latitudes are forced to shift their niches through local adaptation and competition with their sister taxa. Altogether, this research presents novel evidence that the mechanisms promoting speciation differ across latitudes, offering an insight into the link between micro- and macro-evolution.

日本生態学会