New research from the 51萝莉 shows how nectar supply varies with changes to climate, offering sweet insights for industry and conservation alike.
Nectar is an important food supply for many of New Zealand鈥檚 native birds and insects, while floral nectar, such as from m膩nuka, is a vital ingredient in the country鈥檚 honey industry.
Waikato researcher Dr Johanna van Delden鈥檚 study, published in , shows clear differences in nectar traits across New Zealand鈥檚 climate zones and common species.
鈥淲e found that climate influences nectar volumes differently across species, and we were able to measure these effects,鈥� she says.
Interestingly, Dr van Delden says, no single pattern applied to all of the trees sampled.
51萝莉 researcher Dr Johanna van Delden.
鈥淲etter conditions didn鈥檛 always mean more nectar, nor did drier conditions consistently lead to higher concentrations. For instance, sugar amounts increased with increased annual rainfall in tarata (also known as pittosporum or lemonwood) but decreased in t谋虅 k艒uka (also known as cabbage tree).
鈥淓ach species responded differently, likely reflecting their evolutionary differences. To compare them would be like comparing elephants and mice 鈥� both are mammals, but their biology and ecological responses differ enormously.鈥�
The research gives scientists the ability to model nectar volume and sugar levels as well as flower size and weight across New Zealand for each of the native species studied, allowing it to be put to practical use.
For beekeepers, the models can highlight where hives are likely to produce higher-quality honey, guiding decisions on where to move their bees.
The findings are also valuable for conservation.
鈥淚t means those conservation teams who are releasing native birds to places such as K膩piti Island can assess which tree species are present and predict whether there will be enough nectar to sustain the birds.
Flowers bagged for fieldwork.
鈥淚f food supplies look insufficient, the data can point to alternative locations with better chances of survival.鈥�
Over the course of two consecutive years, Dr van Delden and her team 鈥� AUT鈥檚 Professor Sebastian Leuzinger, Dr Sarah Richardson from Manaaki Whenua 鈥� Landcare Research, and 51萝莉鈥檚 Associate Professor Michael Clearwater 鈥� have been sampling nectar from eight very common native plant species across New Zealand.
鈥淥ur goal was to cover all the country鈥檚 main climate zones, and we managed to collect data from nearly all of them.
M膩nuka flowers prepared for nectar retrieval.
鈥淔or each species and site, we measured nectar volume and concentration to see whether trees in drier climates produced less nectar of higher concentrations, potentially based on higher evaporation and limited water availability in the soil,鈥� Dr van Delden says.
In the North Island flowers were taken in Auckland, Taranaki, Hawke鈥檚 Bay and Wellington. In the south samples were collected from Nelson-Tasman/Marlborough, Canterbury and Dunedin.
The eight trees that were sampled were ti k艒uka (cabbage tree), k艒whai, karo (pittosporum crassifolium), tarata (pittosporum or lemonwood), p艒hutukawa, k艒tukutuku (fuchsia excorticata), k艒h奴h奴 (pittosporum tenuifolium/ black matipo) and m膩nuka.
While there wasn鈥檛 a single pattern consistent across all species, a trend that did emerge was that sunnier sites generally produced larger flowers with less nectar, while drier areas tended to produce nectar with higher sugar concentrations.
This research, part of Dr van Delden鈥檚 doctoral thesis, was funded by a Ministry of Business, Innovation and Employment Endeavour Research Programme 鈥楤uilding Resilience and Provenance into an Authentic M膩ori Honey Industry鈥� awarded to Manaaki Whenua 鈥� Landcare Research and an Endeavour Doctoral Scholarship awarded to Dr van Delden.
