A morphological comparison of leaf heteroblasty between New Caledonia and New Zealand

Abstract

Leaf heteroblasty, or pronounced changes in leaf morphology during plant development, is a conspicuous phenomenon on many isolated islands. However, morphological comparisons have not been made between islands, and the processes responsible for island heteroblasty are poorly understood. We investigated differences in leaf morphology of heteroblastic trees and shrubs in New Caledonia and New Zealand. Heteroblastic leaves were collected in field searches in several comparable habitat types in both countries. Leaf area, lobing, and degree of circularity were measured on juvenile and adult leaves from 31 species belonging to 19 plant families. Multivariate analysis of variance was then used to compare ontogenetic changes in leaf morphology between countries. Results showed that juvenile leaves were smaller and more lobed than adult leaves. Life history stage did not interact with country, indicating that morphological shifts between juvenile and adult leaves did not differ between New Caledonia and New Zealand. We conclude that island heteroblasty is similar in both locales, despite their strongly different climates, and the phenomenon likely results from some aspect of their shared geological history.

Vertical gradients in leaf trait diversity in a New Zealand forest

“…Alternatively, it could be associated with herbivory (Rausher 1978). Heteroblasty (i.e., sudden, significant changes in morphology during ontogeny) is a common feature in the New Zealand flora (see Cockayne 1912;Day 1998;Burns and Dawson 2006). Heteroblasty is often attributed to extinct browsing birds (see Givnish et al 1994;Bond et al 2004;Bond and Silander 2007).…”

“…Extant ratites swallow leaves by positioning them in their bill and then snapping their head forwards to orient leaves down their oesophagus, in a manner similar to herons when swallowing fish (Bond et al 2004). Long, narrow leaves could therefore be more difficult for toothless birds to swallow, and are produced by juvenile plants of many heteroblastic species (Burns and Dawson 2006), including two of the three largest tree species studied here (Eleaocarpus dentatus and Knightia exsesa).…”

Evolutionary size changes in plants of the south‐west Pacific

“…Future work would also benefit from considering other archipelagos and perhaps changes in plant traits through ontogeny (e.g. Burns & Dawson, 2006, 2009; Fadzly et al ., 2009).…”

Is crypsis a common defensive strategy in plants? Speculation on signal deception in the New Zealand flora

“…In order to deter bird browsers, plants need other types of defense. [15][16][17][18][19][20] Fadzly et al 12 found that color may have been a critical component of a defensive strategy that evolved in P. crassifolius to deter moa browsing. Spectrographic analyses of seedling leaves from the perspective of birds indicate that their mottled brown color would have made them very difficult for moa to locate amongst a background of leaf litter on the forest floor.…”