Speciation and Extinction

Speciation and extinction are the twin engines that sculpt biodiversity over time. Speciation—the origin of new species—arises when populations become reproductively isolated and diverge through natural or sexual selection, genetic drift or ecological pressures. Isolation may be imposed by geography (allopatry), by habitat or host use (ecological speciation) or even by temporal separation of breeding (allochronic speciation). Genomic studies reveal that the genetic architecture of key traits—ranging from colour patterns to metabolic adaptations—can facilitate divergence even in the face of ongoing gene flow. Extinction—the permanent loss of species—can occur gradually through background processes or catastrophically when environmental change outpaces species’ ability to adapt. Today, human activities have accelerated extinction rates to levels that rival Earth’s greatest mass‐extinction events. Habitat destruction, overexploitation, invasive species, pollution and climate change are eroding populations and whole lineages. Coextinction—whereby the loss of one species triggers the collapse of its dependants—further magnifies biotic loss. Understanding the balance of speciation and extinction, and the processes that tip it, is vital to predict biodiversity trajectories and to guide conservation strategies that maintain evolutionary potential.

Research from Nature Portfolio

A comprehensive meta‐analysis across arthropods, yeast and vertebrates demonstrates that divergent ecological selection generates stronger reproductive isolation than evolution in uniform environments, and that phenotypic plasticity can accelerate premating barriers in early divergence. Contrary to expectations, isolation strength did not correlate simply with elapsed generations, emphasising the role of environment‐induced plastic responses in speciation. In a separate study, the impending loss of Madagascar’s endemic mammals was quantified in evolutionary terms: under natural colonisation and speciation rates, recovering pre‐human diversity would take 1.6 million years for bats and 2.9 million years for non‐flying mammals. Should currently threatened species vanish, those restoration times would more than double. This “evolutionary return time” underscores the deep, long‐lasting impact of recent and imminent extinctions.

Research from all publishers

Analyses of 29,400 terrestrial vertebrate species in the United States identified 515 with fewer than 1,000 individuals, revealing that ongoing population collapses foreshadow a wave of extinctions with cascading ecosystem consequences. More than 94 percent of populations in many of these species have been lost in the past century, highlighting the urgency of targeted conservation. A broad review of cryptic taxa emphasizes that morphologically indistinguishable lineages remain hidden in many groups, complicating conservation planning. Detection of cryptic species requires integrative approaches combining genetic markers, environmental DNA surveys and advanced morphometric techniques; until species are reliably recognised and monitored, protected areas must serve as an interim safeguard. In flora, large‐scale analysis of over a thousand species in a temperate flora showed that hybrid formation is primarily predicted by intrinsic genetic factors—parental genetic distance, phylogenetic position and ploidy level—while geographic overlap and ecological similarity play smaller roles, illustrating how basic genetic compatibilities shape speciation potential.

Speciation and Extinction publication trend

The graph below shows the total number of articles in speciation and extinction across all publications each year (not limited to Nature Index journals).

Technical terms

Allopatric speciation: The evolution of reproductive isolation between populations separated by geographic barriers.

Ecological speciation: The origin of reproductive barriers as a by‐product of adaptation to different environments or resources.

Premating isolation: Barriers that prevent mating or fertilisation, such as behavioural differences or mate choice.

Postzygotic isolation: Mechanisms that reduce the viability or fertility of hybrid offspring after fertilisation.

Coextinction: The secondary extinction of species dependent on a host or mutualist that has itself gone extinct.

Evolutionary return time: The estimated duration needed for natural colonisation and speciation processes to restore lost biodiversity.

Phenotypic plasticity: The capacity of a genotype to produce different phenotypes in response to environmental variation, potentially influencing early steps in speciation.

References

1. Meta-analysis reveals that phenotypic plasticity and divergent selection promote reproductive isolation during incipient speciation. Nature Ecology & Evolution (2025).
2. The macroevolutionary impact of recent and imminent mammal extinctions on Madagascar. Nature Communications (2023).
3. Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction. Proceedings of the National Academy of Sciences of the United States of America (2020).
4. Cryptic species conservation: a review. Biological Reviews (2024).
5. Genetic factors predict hybrid formation in the British flora. Proceedings of the National Academy of Sciences of the United States of America (2023).
6. Has the Earth’s sixth mass extinction already arrived?. Nature (2011).