Pollination activity at an endangered plant species

We are currently researching the pollination requirements/restrictions/deficiencies and other potential threats impacting on an endangered plant species, Astrotricha roddii, Rodd’s Star Hair (Fig. 1), a species that has been in decline for many years in response to droughts and over-grazing by goats. This project is a collaboration between researchers at the University of New England (Australia) and the NSW Department of Planning Infrastructure and Environment.

Figure 1. Astrotricha roddii in its natural habitat, in sclerophyllous woodland on granite in north-western New South Wales.

In November 2020 we visited the only known, vigorous population (fenced off from goats) that was in flower to begin our investigation of the plant’s pollination ecology.
We saw three species of bees at the Astrotricha roddii flowers. The most common species was a species of Leioproctus, currently unidentified; one was a Megachilid species (Fig. 2), yet unidentified; and the third was a small black bee!, probably a Halictid but I saw only one and very briefly – it was eating the pollen into a crop like some Halictids do, so unlikely to be a good pollinator. Oh, there were also some honeybees competing with the native bees at the flowers 😦

Video – Leioproctus sp. bees on Astrotricha roddii

I have never seen so many Leioproctus bees together at the same time! It was amazing! This certainly supports our idea that these bees can survive in stasis underground – as pupae probably – for extended periods (multiple years) to survive through drought periods. We didn’t see these bees before or after the Astrotrichas were in flower. Nor did we see them in the 2019 season, at the height of the drought, but only in 2020 after good rains. Many Leioproctus species are specialists, such as the Persoonia bees, so it is possible these ones we saw on Astrotricha roddii are specialists on this plant species. This species of Leioproctus has been collected only a few times in the past.

Figure 2. A megachilid bee on Astrotricha roddii, with a great load of pollen.

Honeybees caught robbing nectar from a rare grevillea

We saw honeybees robbing nectar from Grevillea masonii recently.

A Feral Honeybee, Apis mellifera, on a Grevillea masonii flower – going nowhere near the pollen presenter or stigma! Photo by Joshua Whitehead.

The actual pollinators we observed were all birds – several species of honeyeater. They didn’t appear to be disturbed by the honeybees feeding in the same shrub. It’s possible though ( as shown in other studies) that the birds had to forage over more plants to get enough food resources owing to the nectar depletion by the honeybees. Perhaps the honeybees actually encouraged more outcrossing as a result – Our breeding system work showed the grevillea to be an obligate outcrossing species so the honeybees could be having an indirect positive effect on seed set….. food for thought and another study.

It seems to be a common problem (if it is a problem) for grevilleas – we’ve seen honeybees stealing nectar from other species such as G. beadleana, another threatened species, seen here (below) in Guy Fawkes River National Park recently:

Apis mellifera feeding on nectar from flowers of Grevillea beadleana. Photo by David Mackay.

Judging by the lack of any pollen remaining on the pollen presenters it appears the real pollinators of this grevillea – shown to be Eastern Spinebill honeyeaters in a study by Caroline L. Gross – are doing a fine job of pollination, and we saw plenty of fruit being set (below) …..

Successful fruit set in Grevillea beadleana. Photo by David Mackay.

… and plenty of seedlings germinating under dead adult plants after recent fire:

Seedlings of Grevillea beadleana germinating under a recently burnt adult plant at Guy Fawkes River National Park, October 2020. Photo by David mackay

Post-fire recovery, June 2020

We have been getting into our sites to assess recovery after the 2019-20 fires (this has often required the 4WD winch and a chainsaw to clear the way in). Superficially, plants appear to be recovering, as in the following image of the main track into Gibratar Range National Park.

Plant recovery beside the main track into Gibraltar Range National Park

This is hardly surprising – the Australian vegetation has been adapting to fire over millions of years. What it may be having problems adapting to, though, is increasing fire frequency. In Gibraltar Range National Park there are areas that haven’t been burnt for over 50 years but this last fire season saw that change.

A large, long-unburnt tree resprouting after the recent fires.


Some of these long-unburnt areas adjoin patches of rainforest that have been protected by these buffer zones but even rainforests suffered in the recent fires. They also suffered in the preceding drought with many species within rainforest patches hit particularly hard, such as these walking stick palms, below.

Walking stick palms suffering from drought

A closer look shows some plants recovering by resprouting, like the eucalypts, and others recovering through seedling germination, like the Gibraltar Range Waratah seedlings below.

Waratah seedlings growing post-fire at Gibraltar Range

Other species show no signs of recovery yet, like Conospermum burgessiorum. We found this single adult (below) but no resprouts and no seedlings where we know there were many plants before the fire. Perhaps it is a species that will germinate in spring?

Conospermum adult. Where are the seedlings?

What I will be particularly interested to see is how the pollinators recover!

A new garden addition

Recently we acquired a new garden addition that came with an unexpected bonus. We bought a Gardenia; but didn’t notice it had at least one passenger – a moth caterpillar! We found out when we saw the adult visiting our Buddlejas 🙂


Cephanodes spp moths are a group of hawkmoths in which the larvae feed on various members of the Rubiaceae family, including Gardenias. The larvae pupate in the soil – maybe that’s how it snuck through! What a beautiful creature to see in our own back yard 🙂

Higher reproductive success by a fig’s pollinator at the fig’s expanding range margin – new paper in J Biogeography

We just published a paper showing pollinators experienced higher levels of reproductive success in isolated trees at a fig species’ expanding range margin, in spite of there being lower numbers of pollinators in these isolated trees (half as many) as there were in larger populations of fig trees. This increase in reproductive success was partly a consequence of parasitoid release (Mackay KD, Gross CL, Ryder DS., Increased reproductive success through parasitoid release at a range margin: Implications for range shifts induced by climate change. J Biogeogr. 2020;00:1–15. https://doi.org/10.1111/jbi.13795).

Ficus rubiginosa female-stage fig with pollinator wasps, Pleistodontes imperialis, entering the narrow opening or ostiole of the fig syconium to pollinate some of the enclosed female flowers and lay their eggs within others. One wasp has already entered, her torn-off wings left sticking out of the ostiole, as another one enters. A pollinator parasitoid, Philotrypesis sp., is sitting on the leaf edge at the lower right. She might be about to lay her own eggs after the pollinators have laid theirs.

The bushfires and the threats to biodiversity

I am starting here with a quote from Jeff Ollerton’s Biodiversity Blog – “A recent assessment by ecologists at the University of Sydney has suggested that almost half a billion reptiles, mammals and birds have been killed so far by the fires.” This assessment by University of Sydney ecologists was made in December before the devastating fires raged through south-eastern NSW and eastern Victoria over the New Year period, so the true figures are likely to have grown substantially since than and will continue to grow over this devastating fire season. Losses of insects, including pollinators, will be even greater. These losses will number in the billions of individuals but what we will never know will be how many locally-endemic species are lost forever, and how much genetic biodiversity is lost in the surviving species. Our lab is working in several areas monitoring pollinator recovery after fire but recovery of both plants and pollinators is being hampered by the ongoing drought conditions. In the Howell Shrubland Endangered Ecological Community, for example, where we have been working since 2007, neither plants nor pollinators are recovering.

Howell Shrubland in a good year
Howell Shrubland nine months after fire in 2019 – without the shrubs! The recovery of this community is being hampered by drought.

We recorded a very low spike of pollinator numbers in the burnt area that correlated with the growth and flowering of very small numbers of fire-ephemeral plants. In fact, we recorded more pollinators in the burnt area than in the adjoining unburnt area (where there were no fire ephemerals and the other plants were not flowering in spite of the fact that it was the normal flowering season). We presented this information at the Ecological Society of Australia meeting in Launceston in November 2019. It will be very interesting to see what recovery occurs once normal rains return.

Insect apocalypse?

The ‘insect apocalypse’ is a theme that has been taken up as a popular discussion point lately, driven in part by recent papers such as ‘Worldwide decline of the entomofauna: A review of its drivers’ by Sánchez-Bayo and Wyckhuys. Those of us who work in this area – entomologists, insect ecologists and others – have been aware of declines in insect abundance and diversity for decades. Unfortunately, because our understanding of these declines is limited there are multiple views, and multiple claims and counter-claims made concerning the geographic and taxonomic extents of these declines; and the discussion has become somewhat emotional at times…like all worthwhile discussions! What I think we can all agree on is that old chestnut: ‘more work needs to be done’. In the meantime, as more work is done and our understanding improves, let’s welcome all the sources of information available and all the different points of view and let’s keep the discussion going!

Pollinator decline

A preprint of a very interesting paper was published this month on the subject of bee decline: Eduardo E. Zattara and Marcelo A. Aizen, Global Bee Decline. Dec. 10, 2019; doi: http://dx.doi.org/10.1101/869784. They found the numbers of collected bee species recorded in global occurrence records sourced from the Global Biodiversity Information Facility have decline today to half of those recorded in the 1950s.

Book launch

A book I did with the poet, John Charles Ryan, has just been launched as an open-access, online book at      https://hdl.handle.net/1959.11/27909 The book is called ‘Between Art and Poetry: New Perspectives on Tablelands Flora’. It is a cross-disciplinary look at the diversity of the vegetation on the New England Tablelands of NSW, Australia. It combines poetry by John, paintings by me, notes on the early botanical exploration of the region by John and environmental-science notes by both of us. We picked out six different ecosystems among the diverse assemblage on the tablelands and explored the flora in those those six systems. Do please have a look and feel free to download/copy/use/cite 🙂

Pollination co-factors


The image above is of Exoneura bicolor on a flower of Leptospermum novae-angliae, the New England Tea-tree. This tea tree (a shrub) is a ‘co-factor’ in the pollination ecology of a threatened species on native mint, Prostanthera staurophylla – known as a co-factor because it provides nectar to pollinators on which P. staurophylla depends and is therefore an important component of P. staurophylla‘s plant-pollinator network. There are only about 100 plants of P. staurophylla left in the wild. We are currently working out the species’ pollination needs and also working closely with the Department of Planning, Industry and Environment on a translocation experiment to establish some back-up populations of this endangered plant.