By Beyond Myrtle Rust.
Myrtle rust is a disease that has been infecting New Zealand’s iconic native myrtles since it arrived in the country in 2017. Researchers have now identified geographical areas (known as ‘refugia’ by ecologists) where species from the plant family Myrtaceae may be able to seek refuge from the fungal pathogen (Austropuccinia psidii) that causes the disease.
“Refugia are often thought of in terms of climate change,” says Dr James McCarthy, an ecosystems and conservation researcher at Manaaki Whenua – Landcare Research. “Refugia are areas where a population of plants or animals might still survive under extreme climate pressures.”
While refugia are not often considered in the context of invasive diseases, the same principles apply. A species may persist if it lives in an area that does not support the disease.
“Where these refugia occur will be different for each species,” says McCarthy, “since each species requires slightly different conditions to survive and thrive.”
McCarthy and colleagues used the New Zealand National Vegetation Survey Databank to determine where myrtles occur and what conditions support which myrtle species. They then used soil, climate and landscape variables to model the full habitat range of each species in New Zealand. Of the 27 Myrtaceae trees, shrubs and vines native to New Zealand, the team was able to gather enough data to establish comprehensive species range predictions for 13 of the species.
Then, they compared how the habitat range of each species overlaps with the likely range of myrtle rust in New Zealand under two scenarios – a ‘core distribution’ scenario representing places where the environment is most suitable for infection and a ‘more severe’ scenario representing the entire known distribution of myrtle rust. Doing this allowed them to identify areas for each myrtle species that could serve as refugia from disease.
“Some species have adequate refugia,” says McCarthy. “Species like southern rātā (Metrosideros umbellata) are almost entirely outside of the predicted extent of myrtle rust.”
For other species, there are few existing refugia.
“This is the case with species like ramarama (Lophomyrtus bullata), which has only 15 km2 of refugia, and swamp maire (Syzygium maire), which has only 1.4 km2 of refugia.”
These refugia could be supplemented with ‘restorable refugia’ – areas that are currently deforested but could become refugia through habitat restoration efforts. McCarthy and colleagues have identified several restorable refugia for different species. However, there are still some species that have neither refugia nor restorable refugia, as their entire probable range overlaps with the predicted range of the disease. For these species, alternative conservation measures may be required.
McCarthy and colleagues have recently published their findings in the Journal of Applied Ecology. Their results will be helpful in informing conservation efforts, including maintaining currently protected refugia, restoring potential refugia, and coming up with alternative conservation methods for species with few refugia options.
While this study tests host and disease habitat range overlap under two disease range scenarios, it does not evaluate these conditions under different climate change scenarios.
“We now need to evaluate how stable these refugia and restorable refugia are in the face of climate change,” says McCarthy.
The question of range and climate is twofold – climate change could alter the natural range of the plants, and it could also shift the range of the disease itself.
“The disease will move much more easily and readily than the plants because it’s caused by a wind-dispersed fungus,” says McCarthy. “While some plants are more easily dispersed than others, they’ll still need to get to a place, germinate, and establish a self-sustaining population in order to fully move into a new area.”
Not only will plant species’ ranges expand more slowly, they will also have to do so under duress from myrtle rust.
“Because myrtle rust attacks young, newly forming plant tissue, survival past that initial germination and young plant stage can be particularly tricky,” says McCarthy.
By modelling the future impacts of climate change on the ranges of each species and on the range of myrtle rust, conservation efforts can be fine-tuned to stay one step ahead of the disease.
Funding for this research was provided by the Ministry for Primary Industries (contract 18607), the Ministry of Business, Innovation and Employment’s Strategic Science Investment Fund, and the Ministry of Business, Innovation and Employment’s Endeavour programme Beyond Myrtle Rust
You can read the journal article here.
Kwa Beyond Myrtle Rust. Myrtle rust ni ugonjwa ambao umekuwa ukiathiri miti ya asili ya New Zealand tangu ulipofika nchini humo mnamo 2017. Watafiti sasa wametambua maeneo ya kijiografia (yajulikana kama'refugia' na wanasaikolojia) ambapo spishi kutoka familia ya mimea ya Myrtaceae zinaweza kutafuta kimbilio kutoka kwa vimelea vya kuambukiza (Austropuccinia psidii) ambayo husababisha ugonjwa huo. "Hifadhi mara nyingi hufikiriwa katika suala la mabadiliko ya hali ya hewa", anasema Daktari James McCarthy, mtafiti wa mifumo ya ikolojia na uhifadhi katika Manaaki Whenua <unk> Landcare Research. "Refugia ni maeneo ambapo idadi ya mimea au wanyama inaweza bado kuishi chini ya shinikizo kali la hali ya hewa. ""Wakati refugia si mara nyingi kuchukuliwa katika muktadha wa magonjwa ya uvamizi, kanuni sawa kutumika." Spishi yaweza kudumu ikiwa huishi katika eneo lisiloweza kuhimili ugonjwa huo. "Mahali ambapo makazi haya yatatokea itakuwa tofauti kwa kila spishi, ""anasema McCarthy, ""kwa kuwa kila spishi inahitaji hali tofauti kidogo ili kuishi na kusitawi. "" McCarthy na wenzake walitumia New Zealand National Vegetation Survey Databank kuamua ambapo myrtles hutokea na ni hali gani zinazounga mkono spishi gani za myrtle. """ Kisha walitumia udongo, hali ya hewa na mabadiliko ya mandhari kuiga eneo kamili la makazi ya kila spishi huko New Zealand. Kati ya miti 27 ya Myrtaceae, vichaka na mizabibu ya asili ya New Zealand, timu hiyo iliweza kukusanya data ya kutosha kuanzisha utabiri wa kina wa aina za mimea 13 ya mimea hiyo. Kisha, walilinganisha jinsi eneo la makazi ya kila spishi linavyolingana na eneo linalowezekana la kutu ya myrtle huko New Zealand chini ya hali mbili - hali ya "usambazaji wa msingi" inayowakilisha maeneo ambapo mazingira yanafaa zaidi kwa maambukizi na hali ya "mzito zaidi" inayowakilisha usambazaji wote unaojulikana wa kutu ya myrtle. Kwa kufanya hivyo, waliweza kutambua maeneo ambayo kila spishi ya mti huo ingeweza kukimbilia ili kuepuka magonjwa. "Nafasi fulani zina makao ya kutosha", asema McCarthy. "Aina kama vile rātā ya kusini (Metrosideros umbellata) ni karibu kabisa nje ya kiwango cha utabiri wa kutu ya myrtle. " Kwa spishi nyingine, kuna makazi machache yaliyopo. "Hii ni kesi na spishi kama vile ramarama (Lophomyrtus bullata), ambayo ina 15 km2 tu ya refugia, na swamp maire (Syzygium maire), ambayo ina 1.4 km2 tu ya refugia. ""Hizi refugia inaweza kuongezwa na ""refugia kurudishwa"" maeneo ambayo kwa sasa ni deforested lakini inaweza kuwa refugia kupitia juhudi za kurudisha makazi." McCarthy na wenzake wametambua makazi kadhaa yanayoweza kurudishwa kwa spishi tofauti. Hata hivyo, bado kuna baadhi ya spishi ambazo hazina refugia wala refugia inayoweza kurudishwa, kwani eneo lao lote linalowezekana linafanana na eneo linalotarajiwa la ugonjwa huo. Kwa spishi hizi, hatua mbadala za uhifadhi zinaweza kuhitajika. McCarthy na wenzake wamekuwa wakichapisha matokeo yao katika jarida la Applied Ecology. Matokeo yao yatasaidia katika kuelimisha juhudi za uhifadhi, ikiwa ni pamoja na kudumisha makazi ya sasa yaliyohifadhiwa, kurudisha makazi ya uwezekano, na kuja na mbinu mbadala za uhifadhi kwa spishi zilizo na chaguzi chache za makazi. Ingawa utafiti huu unajaribu makazi ya mwenyeji na ugonjwa wa ugonjwa chini ya hali mbili za ugonjwa, haichunguzie hali hizi chini ya hali tofauti za mabadiliko ya hali ya hewa. "Sasa tunahitaji kutathmini jinsi makazi haya ya makazi na makazi yanayoweza kurudishwa yanavyoweza kukabiliana na mabadiliko ya hali ya hewa", anasema McCarthy. Swali la eneo la kuenea na hali ya hewa ni la mara mbili - mabadiliko ya hali ya hewa yanaweza kubadilisha eneo la asili la mimea, na pia inaweza kubadilisha eneo la ugonjwa wenyewe. "Ugonjwa huo utaenea kwa urahisi zaidi kuliko mimea kwa sababu unasababishwa na kuvu zinazosambazwa na upepo", anasema McCarthy. Ingawa mimea fulani huenea kwa urahisi kuliko nyingine, bado itahitaji kufika mahali fulani, kuchipuka, na kuanzisha idadi ya mimea inayojihifadhi ili kuhamia eneo jipya. "Kwa sababu kutu ya myrtle hushambulia tishu za mimea vijana, zinazojitokeza hivi karibuni, kuishi baada ya hatua hiyo ya mwanzo ya kuota na hatua ya mimea midogo inaweza kuwa ngumu sana", anasema McCarthy. Kwa kuunda mfano wa athari za baadaye za mabadiliko ya hali ya hewa kwenye maeneo ya kila spishi na kwenye eneo la kutu ya myrtle, juhudi za uhifadhi zinaweza kusawazishwa ili kubaki hatua moja mbele ya ugonjwa. Utafiti huu ulifadhiliwa na Wizara ya Viwanda vya Msingi (mkataba wa 18607), Wizara ya Biashara, Ubunifu na Ajira (Strategic Science Investment Fund) na Wizara ya Biashara, Ubunifu na Ajira (Endeavour) na mpango wa Beyond Myrtle Rust.