Floral colours in a world without birds and bees: the plants of Macquarie Island

Abstract

We studied biotically pollinated angiosperms on Macquarie Island, a remote site in the Southern Ocean with a predominately or exclusively dipteran pollinator fauna, in an effort to understand how flower colour affects community assembly. We compared a distinctive group of cream-green Macquarie Island flowers to the flora of likely source pools of immigrants and to a continental flora from a high latitude in the northern hemisphere. We used both dipteran and hymenopteran colour models and phylogenetically informed analyses to explore the chromatic component of community assembly. The species with cream-green flowers are very restricted in colour space models of both fly vision and bee vision and represent a distinct group that plays a very minor role in other communities. It is unlikely that such a community could form through random immigration from continental source pools. Our findings suggest that fly pollination has imposed a strong ecological filter on Macquarie Island, favouring floral colours that are rare in continental floras. This is one of the strongest demonstrations that plant-pollinator interactions play an important role in plant community assembly. Future work exploring colour choices by dipteran flower visitors would be valuable.

Pollinator Diversity: Distribution, Ecological Function, and Conservation

“…The same is probably true for the lizards, particularly on oceanic islands (Olesen and Valido 2003) where plants have a tendency to evolve interactions with pollinators that are rather different to their mainland relatives (e.g. Shrestha et al 2016). …”

Ginger and the beetle: Evidence of primitive pollination system in a Himalayan endemic alpine ginger (Roscoea alpina, Zingiberaceae)

“…Indeed, the spectral data in Fig 2 does not have characteristics of ‘red’ flowers which should possess a sharp change in reflectance of greater than 20% over a 50nm region of the spectrum [36,37] as have been associated with bird pollinated red flowers [58] and suggested for beetle pollinated red flowers based upon colour categories [12]. The flower spectra possess a sharp change in spectral reflectance for wavelengths less than 420nm; which was not a characteristic of the flowers of Macquarie Island where pollination appears to be mediated by flies [35]. The flower spectral is also unusual in that it reflects a lot of UV and longer wavelength radiation, a characteristic that is not consistent with bee pollinated flowers [59–61], but the strong change in reflectance is indicative of an evolved signal to a pollinator [58,62].…”

“…alpina (at Poonhill) to provide initial insights into whether flower spectra might play a role in signal evolution for this species. Specifically, recent work [35] shows that in the absence of mainstream pollinators that are common in most floral communities, flowers from remote Macquarie Island deep in the southern ocean are a dull cream-green colour, and lack any sharp change in reflectance at wavelengths less than about 420nm. We thus used this as a comparison point for recorded spectra from R .…”

Trait patterns across space and time suggest an interplay of facilitation and competition acting on Neotropical hummingbird‐pollinated plant communities

“…In these communities, there is a higher proportion of hermit-specialized plant species than in coastal lowland communities (57% in ITA and 55% in SVG versus 29% in PIC, Wolowski et al 2013, Maruyama et al 2015, Vizentin-Bugoni et al 2016). Thus, the trait signature on these communities may reflect the role of biological filter played by hermit hummingbirds, favoring plants with some specific floral traits (Shrestha et al 2016). For instance, anther and stigma height were higher on average for montane than lowland communities (in mm; ITA: 36.19 and 37.89, SVG: 39.…”

“…Many plant species depend on pollinators for their reproduction (Ollerton et al 2011), and can only persist in a community in the presence of such mutualists (Lundgren et al 2016). In this scenario, only the plant species with reproductive traits fitting the local pollinator community will persist, implying that pollinators act as biotic filters (Shrestha et al 2016). Plants also influence each other's fitness through pollinator sharing (Sargent et al 2011), leading to the possibility of competitive exclusion, or stabilizing niche differences, structuring plant communities (HilleRisLambers et al 2012, Nottebrock et al 2016.…”