Abstract Temperate mesic to damp grasslands were long viewed as seminatural habitats, established after forest clearance by humans and since then maintained by agricultural techniques. An issue unanswered under this view is the origin of diverse and specialised grassland biota, including European large blues of the genus Phengaris (Lycaenidae). These butterflies have been much studied owing to their myrmecophilous relationships with Myrmica ants, narrow habitat specificity, and threatened status. Phengaris nausithous, the most common Phengaris in Central Europe, inhabits damp to mesic meadows with representation of the initial larval host plant, Sanguisorba officinalis, and the ants Myrmica rubra (the most frequent host), M. scabrinodis and M. ruginodis. It displays close association with edges or small meadow patches, avoiding spacious uniformly managed units. Based on extensive ants trapping at the Oder river alluvial meadows, the Czech Republic, we demonstrate that the Myrmica host ants are absent from interiors of large and uniformly mown meadows, probably being outcompeted by numerically and ecologically dominant Lasius niger ant. The preferences of P. nausithous for edges is likely mediated by adult movement behaviour and had presumably evolved in mosaic landscapes with alternating wooded and grassland structures, arguably a common land cover in pre-Homo sapiens Europe. Implications for insect conservation The relationships between P. nausithous and its Myrmica hosts certainly did not evolve in spacious homogeneously managed grasslands. Land cover types that retained the structure of temperate pre-Homo savannas, originally established by interaction between vegetation and herbivorous megafauna (Pearce et al. <CitationRef CitationID="CR52">2023</CitationRef>, <CitationRef CitationID="CR53">2025</CitationRef>) and long maintained by traditional agropastoralism, are still locally present across temperate Europe. Perhaps due historical or geographic reasons, they do not even share a generally accepted name, being labelled as wood pastures, wooded grasslands, sparse woodlands, or parklands. Owing to small-scale heterogeneity of conditions, they represent some of the species-richest sites botanically (Chytrý et al. <CitationRef CitationID="CR10">2015</CitationRef>; Roleček et al. <CitationRef CitationID="CR61">2025</CitationRef>) and entomologically (Bonari et al. <CitationRef CitationID="CR4">2017</CitationRef>). In “wood pasture” habitats in Hungary, mosaics of woody and grassland structures prevent competitive exclusion of subordinate ant species, which creates ant mosaics displaying much higher diversity than homogenous habitats (Lőrincz et al. <CitationRef CitationID="CR43">2024a</CitationRef>,<CitationRef CitationID="CR44">b</CitationRef>). Due to naturally high vegetation productivity of alluvial habitats, only a few such savanna-like landscapes have been preserved in lowlands suitable for P. nausithous. The strict preference of this butterfly for woody edges, temporarily neglected grassland patches, and small grassland lots in villages and suburban settings (Kajzer-Bonk et al. <CitationRef CitationID="CR35">2016</CitationRef>, <CitationRef CitationID="CR33">2022</CitationRef>) represent a legacy of the spatial structure of past alluvial habitats. Until the ecological proceses that had modelled European alluvia in a deep past are restored, conserving P. nausithous requires focusing on such marginal habitats.

Vast alluvial meadows fail to provide habitats to host ants of the butterfly Phengaris nausithous along upper Oder river

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发表日期：

2026年2月23日

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Pavel Pech,
Martin Konvička,
Lukáš Spitzer

摘要

Abstract

Temperate mesic to damp grasslands were long viewed as seminatural habitats, established after forest clearance by humans and since then maintained by agricultural techniques. An issue unanswered under this view is the origin of diverse and specialised grassland biota, including European large blues of the genus Phengaris (Lycaenidae). These butterflies have been much studied owing to their myrmecophilous relationships with Myrmica ants, narrow habitat specificity, and threatened status. Phengaris nausithous, the most common Phengaris in Central Europe, inhabits damp to mesic meadows with representation of the initial larval host plant, Sanguisorba officinalis, and the ants Myrmica rubra (the most frequent host), M. scabrinodis and M. ruginodis. It displays close association with edges or small meadow patches, avoiding spacious uniformly managed units. Based on extensive ants trapping at the Oder river alluvial meadows, the Czech Republic, we demonstrate that the Myrmica host ants are absent from interiors of large and uniformly mown meadows, probably being outcompeted by numerically and ecologically dominant Lasius niger ant. The preferences of P. nausithous for edges is likely mediated by adult movement behaviour and had presumably evolved in mosaic landscapes with alternating wooded and grassland structures, arguably a common land cover in pre-Homo sapiens Europe.

Implications for insect conservation

The relationships between P. nausithous and its Myrmica hosts certainly did not evolve in spacious homogeneously managed grasslands. Land cover types that retained the structure of temperate pre-Homo savannas, originally established by interaction between vegetation and herbivorous megafauna (Pearce et al. 2023, 2025) and long maintained by traditional agropastoralism, are still locally present across temperate Europe. Perhaps due historical or geographic reasons, they do not even share a generally accepted name, being labelled as wood pastures, wooded grasslands, sparse woodlands, or parklands. Owing to small-scale heterogeneity of conditions, they represent some of the species-richest sites botanically (Chytrý et al. 2015; Roleček et al. 2025) and entomologically (Bonari et al. 2017). In “wood pasture” habitats in Hungary, mosaics of woody and grassland structures prevent competitive exclusion of subordinate ant species, which creates ant mosaics displaying much higher diversity than homogenous habitats (Lőrincz et al. 2024a,b). Due to naturally high vegetation productivity of alluvial habitats, only a few such savanna-like landscapes have been preserved in lowlands suitable for P. nausithous. The strict preference of this butterfly for woody edges, temporarily neglected grassland patches, and small grassland lots in villages and suburban settings (Kajzer-Bonk et al. 2016, 2022) represent a legacy of the spatial structure of past alluvial habitats. Until the ecological proceses that had modelled European alluvia in a deep past are restored, conserving P. nausithous requires focusing on such marginal habitats.