Leaf mining is a form of endophagous herbivory in which insect larvae live and feed within leaf tissue. In this review we discuss aspects of leaf miner ecology, and the current evidence for three hypotheses relating to the evolution of this feeding guild. We also present a summary of the literature coverage relating to these herbivores, which have been relatively poorly studied compared with insects that feed externally such as sap suckers and leaf chewers.

Leaf miners are insects whose larval stages live between layers of leaf epidermis, feeding on mesophyll and lower epidermis to create mine-like cavities. Little is known about the ecology or distribution of leaf miners in Australia. We investigated the incidence of leaf miners in relation to aridity, vegetation types, host plant taxonomy, leaf traits, canopy cover and latitude. We surveyed leaf miners at 15 sites in NSW, eastern Australia, situated along a rainfall gradient from 300 to 1700 mm per annum and a latitudinal gradient of 28°S to 33°S, within four vegetation types (mallee, heath, woodland and rainforest). Leaf mining was recorded from 36 plant species, 89% of which had no previous record of mining.The proportion of mined plant species at each site varied, but there was no significant difference between vegetation types. Leaf mining presence was positively correlated with both total leaf length and leaf thickness. No significant correlations were found between the proportion of mined species at a site and rainfall, latitude or foliar projected cover. We conclude that leaf mining is a widespread type of insect herbivory whose distribution patterns are more likely to be influenced by biotic than abiotic factors.

1. Leaf mining insects feed within plant tissue and thus have close physical associations with their host plants. Little is known about the evolution of relationships between leaf miners and their host species.2. The prevalence of leaf mining was examined in relation to the phylogeny of a dominant family of Australian plants, the Myrtaceae. Sixty-eight species from the 10 major phylogenetic groups within the family were sampled in south-eastern Australia.3. Fifty-seven per cent of the plant species examined were found to be mined. Several leaf traits were compared between mined and unmined plant species to investigate the potential role of both physical and nutritional characteristics in determining host-plant susceptibility to these herbivores.4. The physical leaf traits measured were leaf area, specific leaf area (SLA), lamina thickness, toughness, and amount of fibre (percentage hemicellulose). The nutritional traits were water content, and concentrations of carbon, nitrogen, total phenols and condensed tannins. Principal component analysis showed mined plant species differed from unmined in terms of several leaf traits.5. In a post hoc regression weighted for phylogeny, leaf miner presence was significantly positively correlated with plant species having thinner laminas and higher phenol concentrations, and was positively correlated with marginal significance to SLA and water content.