Teaching an Old Bird New Tricks: assisting the evolution of native species through selective breedingPosted: April 30, 2018
Figure 1: A rat preying on a nesting bird
By Rachel Selwyn
We’ve bred dogs to herd sheep, to point out hunting prey…can we breed NZ native species to fight back against introduced predators? Assisted evolution is a controversial conservation tactic but it’s not as far-fetched as you might think.
Native species on island ecosystems like in New Zealand have evolved for thousands of years without mammalian predators and without the appropriate predator avoidant behaviors1. The arrival of exotic predators like rats, stoats, and possums found the native species defenseless and had catastrophic effects on their populations2-4. In response, New Zealand has undertaken extensive eradication and predator control efforts which have helped species such as the North Island robin5-7.
Unfortunately, predator control has several flaws including the difficulty and high cost of achieving 100% eradication across the whole country8-9, the risk of unintended ecological effects10, questionable ethics11, and the never-ending battle against reintroductions12-13. Eradicating several species across an entire landmass is a massive undertaking especially given the difficulty monitoring international borders sufficiently to prevent reintroduction events. An alternative approach is to help native species adapt to the presence of new predators, through selective breeding, to create a sustainable coexistence of predator and prey.
The underlying issue in New Zealand is the prey naïveté, or lack of antipredator behavior, of native fauna that have not had the opportunity to adapt to the presence of these new predators14. Encouraging evolutionary adaptations to arise in the native fauna through selective breeding provides an alternative solution that does not involve large-scale extermination of an entire class of species.
Figure 2: A graphic depicting the process of selectively breeding a plant species for desired increased plant height.
Humans have used selective breeding for thousands of years, choosing desirable traits in agricultural plant species and domestic animals15. Selective breeding does not just apply to physical characteristics. Domesticated dogs are an example of using this technique to promote desirable behaviors such as pointing in hunting breeds and herding in sheepdogs16. Some conservationists are advocating for selective breeding to be similarly used for wild species to choose adaptive behaviors like predator avoidance to counteract prey naïveté17. Identifying individuals from a population that demonstrate the desired behavior or characteristic and selectively breeding them together increases the prominence of this trait in the population, as seen in Figure 2. Beneficial predator avoidant traits would ordinarily develop over time through natural selection, however, it can take a long time and high levels of predation often wipe out native populations before they have a chance to adapt18. As humans are responsible for the dramatic scale of invasions around the world, it is our responsibility to help native species adapt to the changes we have provoked.
Some anti-predator traits have begun to arise in some New Zealand species although the frequency of these traits remains too low to effectively protect them. The New Zealand bellbird (Anthornis melanura) has begun decrease parental activity during nesting periods when predators are present in their habitat19. This behavior is believed to be adaptive as high parental activity at a nest can attract predators and lead to higher predation rates. Identifying adaptive behaviors like this would allow conservationists to deliberately breed the individual bellbirds showing this behavior and effectively speed up the process of natural selection.
Selective breeding to modify wild populations has been conducted in the past including with the plains zebra20 and with largemouth bass21. Selective breeding is currently being considered in marine conservation with species of corals and their symbionts. Researchers working to determine the genetic link within heat-tolerant corals hope to promote this trait in coral populations making them more resistant to climate change22-23.
How could we apply this to New Zealand? Kiwis couldn’t realistically be bred to fly away from predators without significantly altering them from a well-loved species. Species like the kiwi could be bred to encourage protective strategies that improve their ability to survive alongside novel predators. Captive breeding programs that are already in place, like those with the kakapo and takahe24, could be supplemented with selective breeding trials. Selective breeding would have to take place amongst all naïve prey simultaneously to avoid predators simply switching to easier less adapted prey25. Assisting evolution in New Zealand species would involve a widespread and costly effort over many years, however, this option provides a definite solution compared to the never-ending fight of eradication efforts. Critics are concerned that selective breeding for a single trait could lead to loss of genetic diversity within the population and magnification of harmful alleles26. While loss of genetic diversity is a risk with captive breeding, continually supplementing breeding efforts with individuals from the larger wild population will minimize this issue. Selective breeding may not succeed equally amongst all species so it is vital that trials are conducted in isolation with predator control maintained in wild populations.
Assisting evolution through selective breeding is a controversial and radical solution to prey naïveté that has the potential to replace predator eradication efforts. This should be conducted alongside predator control initially to provide time for adaptations to persist. There are several risks associated with this approach that merit further investigation, however, the benefit has more weight as successfully assisting native species to coexist alongside introduced predators would be a monumental conservation success. Current predator control efforts will need to continue forever to protect New Zealand’s native species, however, by selectively breeding naïve species to hold their own we can one day achieve ecosystems that can sustain themselves without human intervention.
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- O’Donnell, C.F.J., Weston, K.A., Monks, J.M. (2017). Impacts of introduced mammalian predators on New Zealand’s Alpine Flora. New Zealand Journal of Ecology 41(1):1-22
- Armstrong, D.P.(2016). Population responses of a native bird species to rat control. The Journal of Wildlife Management 81(2):342-346.
- Starling-Windhof, A., Massaro, M., Briskie, J. (2011). Differential effects of exotic predator-control on nest success of native and introduced birds in New Zealand. Biological Invasions 13(4):1021-1028
- Whitehead, A.L., Edge, K.A., Smart, A.F., Hill, G.S., Willans, M.J. (2008). Large scale predator control improves productivity of rare New Zealand riverine duck. Biological Conservation 141(11):2784-2794.
- Anderson, D.P., Gormley, A.M., Ramsey, D.S.L., Nugent, G., Martin, P.A.J., Bosson, M., Livingston, P., Byrom, A.E. (2017). Bio-economic optimisation of surveillance to confirm broadscale eradications of invasive pests and diseases. Biological Invasions 19(10):2869-2884.
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- Keller Kopf, R., Nimmo, D.G., Humphries, P., Baumgartner, L.J., Bode, M., Bond, N.R., Byrom, A.E., Cucherousset, J., Keller, R.P., King, A.J., McGinness, H.M., Moyle, P.B., Olden, J.D. (2017). Confronting the risks of large-scale invasive species control. Nature Ecology & Evolution 1
- Souther, C.E.(2016). The Cruel Culture of Conservation Country: Non-Native Animals and the Consequences of Predator-Free New Zealand. Transnational Law & Contemporary Problems 26(1):63-119.
- Russell, J.C., Brown, P.H., Byrom, A.E.(2015). Predator-free New Zealand: Conservation Country. BioScience 65(5):520-525.
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- Akey, J.M., Ruhe, A.L., Akey, D.T., Wong, A.K., Connelly, C.F., Madeoy, J., Nicholas, T.J., Neff, M.W. (2010). Tracking footprints of artificial selection in the dog genome. PNAS 107(3):1160-1165.
- Akaad, D.A., Gerding, W.M., Gasser, R.B., Epplen, J.T. (2015). Homozygosity mapping and sequencing identify two genes that might contribute to pointing behavior in hunting dogs. Canine Genetics and Epidemiology 2:5.
- Moseby, K.E., Blumstein, D.T., Letnic, M. (2015). Harnessing natural selection to tackle the problem of prey naïveté. Evolutionary Applications 9(2):334-343.
- Owens, I.P.F., Bennett, P.M. (2000). Ecological basis of extinction risk in birds: Habitat loss versus human persecution and introduced predators. PNAS 97(22):12144-12148.
- Massaro, M., Starling-Windhof, A., Briskie, J.V., Martin, T.E. (2008). Introduced Mammalian Predators Induce Behavioral Changes in Parental Care in an Endemic New Zealand Bird. PLoS ONE 3(6):2331.
- Harley, E.H., Knight, M.H., Lardner, C., Wooding, B., Gregor, M. (2009). The Quagga project: progress over 20 years of selective breeding. South African Journal of Wildlife Research 39(2):155-163.
- Garrett, G. (2002). Behavioral modification of angling vulnerability in Largemouth bass through selective breeding. Black bass: ecology, conservation, and management. American Fisheries Society, Editors: D. P. Philip and M.S. Ridgeway. 387-392.
- Baums, I.B. (2008). A restoration genetics guide for coral reef conservation. Molecular Ecology 17(12):2796-2811.
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- Clout, M.N., Craig, J.L. (1995). The conservation of critically endangered flightless birds in New Zealand. International Journal of Avian Science 137(s1):181-190.
- Kjellander, P., Nordstrom, J. (2003). Cyclic voles, prey switching in red fox, and roe deer dynamics- a test of the alternative prey hypothesis. Oikos 101(2): 338-344.
- Miller, P.S. (1995). Selective breeding programs for rare alleles: examples from the przewalski’s horse and California condor pedigrees. Conservation Biology 9(5):12621273.
By Olivia Quigan
Restoration is becoming an increasingly useful tool in conservation. We can now bring biodiversity back to an area that has been impaired beyond recognition by human activities, such as logging, damming, or open cast mining. Given that we are restoring more and more ecosystems around the world, does this give us leave to destroy ‘pristine’ habitats in order to exploit them to gain access to resources?
The benefits of destroying habitats in order to access resources are mostly of economic value. When cost-benefit analyses for an open cast mine are done, the only environmental outcomes that are considered are those that can be turned into a monetary value (Abelson, 2015). These are quantified as the physical impacts on the environment and how these impact health and agriculture (Abelson, 2015). This ignores the intrinsic value of unique species, as through losing them we reduce global biodiversity – a value that cannot be measured in currency (Campbell, 2014).
An argument could be made for destruction of habitats with a view to restoration, that given enough planning time, species can be saved before the habitat loss occurs. They could then be returned to the habitat during the restoration process, or found suitable homes elsewhere, that are similar to their current habitat. Translocation can be a valid restoration method, however not without its risks. This method was attempted in 2011. To allow for an open cast mine in New Zealand’s South Island, the unique and endemic Powelliphanta augusta Snails were collected and stored in shipping containers with the ultimate goal of introducing them to nearby forests. This resulted in the deaths of 800 individuals due to a technical failure of the refrigeration unit they were stored in (Vallance, 2011). This attempt was a failure, because even with the remaining snails being translocated, they are not
successfully persisting in their new environment, with death rates at new sites of up to thirty per cent (Morris, 2010). There are many other instances of failed translocations. Analyses of many reptile and amphibian translocations between 1991 and 2006 showed that up to 30 per cent of translocations failed in producing self-sustaining populations (Germano & Bishop, 2008). This rate of failure must force us to come to the conclusion that we do not yet have the knowledge to prevent extinctions in the case of a planned environmental degradation, especially when endemic species are involved, as the risk is often too high to justify needless environmental degradation.
The creation of novel landscapes is an inevitable outcome of the anthropogenic influence on the world. As we remove natural habitats, the areas that replace them won’t be the same; no matter how hard we try to restore them. A study by Lugo, Carlo and Wunderle Jr. (2011) looked at the islands of Puerto Rico and the introduced species there.
The forest cover here dropped from 100 per cent to just six per cent by the 1940s. The restoration of much of the forest has included many introduced species, both plants and animals. The resulting forest was a mixture of both, but the native plant species continue to dominate the forests, with cover of over 80 per cent. Native birds continue to be successful, and forage on both natives and introduced plants. The introduced honeybee appears to have adapted to the phenology of the native plants and is an important pollinator (Lugo, Carlo, & Wunderle Jr., 2012). This indicates that novel habitats created by restoration efforts can be sustained with introduced species, but we must continue to protect the native species to ensure lasting intrinsic value of the ecosystem.
Disturbed habitats are more likely to be susceptible to invading species. These are defined as species which “proliferate and noticeably replace native species,” (Clewell & Aronson, 2013). Invasive species with a more generalist way of life will have an advantage over native species, especially if these species have evolved into a more specialist niche (Clewell & Aronson, 2013). This is even more applicable in island habitats, where animals have evolved with limited predators. Using the land for agriculture or industry changes the scope of the ecosystem, and increases the vulnerability of it to invasions from non-native species (Vitousek, D’Antonio, Loope, Rejmanek, & Westbrooks, 1997). Human modification of environments is a major driver the invasion by non-native species. Logged forests in Thailand that were home to an invasive weed experienced an eight-fold reduction in pollinators visiting native species. The invasive beetle, Coccinella septempunctata, showed higher abundances in agricultural grasslands when compared to non-modified areas (Didham, Tylianakis, Gemmell, Rand, & Ewers, 2007). Due to the precious value of native species, the total destruction of a habitat cannot be justified as this disturbance leads to increased vulnerability to species invasions.
The complete destruction of a habitat will always be detrimental to the species living there. To destroy a habitat for monetary gain is to place a value on the uniqueness of habitats, and deem it less important than the economy. The evidence shows that we are not capable of maintaining the integrity of a habitat if we destroy it completely. Disturbed habitats are more likely to allow invasive species, which decimate native populations. Human attempts at preservation by translocation of species often fail. As we cannot guarantee the safety of our unique species, we cannot justify the destruction of any habitat; regardless of how accomplished we are becoming at restoring them.
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Campbell, R. (2014). Seeing through the dust: Coal in the Hunter Valley Economy. Canberra: The Australia Institute.
Clewell, A. F., & Aronson, J. (2013). Ecological Restoration – Principles, Values & Structure of an Emerging Profession (2nd ed.). Washington, D.C: Island Press.
Didham, R. K., Tylianakis, J. M., Gemmell, N. J., Rand, T. A., & Ewers, R. M. (2007). Interactive effects of habitat modification and species invasion on native species decline. Trends in Ecology and Evolution, 22(9), 489-496.
Germano, J. M., & Bishop, P. J. (2008). Suitability of Amphibians and Reptiles for Translocation. Conservation Biology, 7-15.
Lugo, A. E., Carlo, T. A., & Wunderle Jr., J. M. (2012). Natural mixing of species: Novel plant-animal communities on Caribbean Islands. Animal Conservation, 233-241.
Morris, R. (2010). An Unfortunate Experiment. Forest And Bird, 14-16.
Vallance, N. (2011, November 10). Snail fridge deaths an avoidable tragedy. Retrieved from Forest and Bird: http://www.forestandbird.org.nz/what-we-do/publications/media-release/snail-fridge-deaths-avoidable-tragedy
Vitousek, P. M., D’Antonio, C. M., Loope, L. L., Rejmanek, M., & Westbrooks, R. (1997). Introduced Species: A significant component of Human-caused Global Change. New Zealand Journal of ecology, 1-16.
The Invasion/Conservation Paradox: What happens when an invasive species is also a threatened species? – Mary F. PaulPosted: May 5, 2014
In conservation, the term non-native tends to evoke a knee-jerk association with the keywords: unwanted, invasion, eradication, pest. Particularly here in New Zealand, the experience with introduced species has been extremely negative, resulting in the loss of many species and the complete disruption of an ecosystem.
The line between introduced species and invasive species has proven difficult to define as (like many terms in ecology) the definition can be ambiguous and open to subjective interpretation (Colautti & MacIsaac, 2004). Some define invaders broadly as a widespread non-indigenous species, whilst others limit the term to species that adversely affect habitats economically and ecologically (Colautti & MacIsaac, 2004; IUCN, 2013).
Invasive species are one of the three main threats to global biodiversity, along with habitat loss and climate change. The introduction of new species to a non-native ecosystem can have devastating flow-on effects throughout the community and can result in both environmental and economic damages.
But what happens when a species is considered invasive in one area of the world but considered threatened in another?
There are several examples of both plant and animal taxa which have been successful invaders of new locations yet are experiencing declines in their native habitat. As climates continue to shift, this may become a more and more frequent occurrence when native areas become less suitable and new climatic envelopes in non-native areas become accessible. Brook trout, Monterey Cypress, and Chinese wattle-necked softshell turtles highlight these paradoxes. All three of these have managed to become established in island settings where introductions can be particularly consequential.These examples also raise questions about ex situ conservation, or practicing conservation through relocation, and weighing the costs of an introduced species and deciding whether or not to preserve them outside their native range.
Brook trout (Salvelinus fontinalis) are a species of char native to eastern North America, inhabiting clear, cool freshwater lakes, rivers, streams, and ponds. While their historic range is limited to the East coast of the United States and Canada, they have been introduced to over 47 countries spanning Europe, South America, Africa and Oceania where they are classified as an invasive and damaging species (ISSG, 2014).
Originally introduced to provide recreational and commercial fishing, not all introductions led to establishment but populations are now present throughout the United States, Europe, and New Zealand (EBTJV, 2013). There are many cases of brook trout out competing native species in introduced regions. Non-native brook trout displace bull trout (Salvelinus confluentus) at high elevations within introduced areas throughout the western United States and Canada (Rieman et al., 2006; Warnock & Rasmussen, 2013).
In their native range extending from southern Canada to South Carolina, habitat fragmentation, invasive species, and climate change are causing declines in brook trout populations. Ironically, non-native fish rank as the largest biological threat to brook trout (EBTJV, 2013). Declines in brook trout in native areas have been observed due to interspecific competition and predation on juveniles by brown trout (Salmo trutta) (Fausch & White, 1981). Increased sedimentation and runoff are likely to be contributing factors to the diminished populations, with higher water temperatures due to industrial runoff and climate change driving the populations to higher elevations. Climate change will continue to restrict the native range of the brook trout, increasing minimum elevation by up to 714 m in the southern native boundary, meaning further reduction of populations within native habitats (Meisner, 1990).
Monterey Cypress (Cupressus macrocarpus) is a species of cypress native to California that thrives in mild and humid climates. The historic distribution of Monterey Cypress forests once spanned the1400 kilometer-long stretch of the California coast from Marin County to Baja California (Graniti, 1998).
The present native distribution is now restricted to a dismal 3.2 kilometer strip on the Monterey Peninsula, where only two relict populations remain (Farjon, 2013). According to the IUCN Red List, the species is classified as threatened and vulnerable with the main forces of the reductions being fire damage and the spread of fungal disease (Farjon, 2013). Cypress canker (Seiridium cardinale), a pathogenic fungus, attacks trees in the cypress family by causing girdling cankers and eventually death of the tree (Graniti, 1998).
While the populations in it’s native territory are dwindling, Monterey Cypress has managed to successfully establish elsewhere. Macrocarpa has been introduced all over the world for use as ornamental trees, windbreaks, and timber (Graniti, 1998). One of the most notable introduction was to New Zealand, where populations flourish. Monterey Cypress was introduced to New Zealand in the 1860s and has since naturalized, finding the climate to be more suitable than that of its native habitat (Wassilleff, 2013). But even in New Zealand, Monterey Cypress has suffered losses due to the spread of cypress canker, causing it to lose popularity for use as timber (Farjon, 2013). Despite the influx of canker in the 1970s, Monterey Cypress still persists throughout rural New Zealand (NZPCN, 2010).
Chinese wattle-necked softshell turtles
The native range of the Chinese wattle-necked softshell turtle (Palea steindachneri) is from the Guangdong region in China down to northern Vietnam. The species is established on Mauritius and the Hawaiian islands Kauai and Oahu, thriving in the warm climate (Ernst & Lovich, 2009). Brought over in the 1800s by Chinese immigrants as a food source, the species has been long established, yet little is known about their present abundance (McKeown & Webb, 1982).
P. steindachneri is an introduced species, and is considered to be potentially invasive, although little is known about their impact and there has been limited research into the ecology and behaviour of the species (Engstrom, 2013; Ernst & Lovich, 2009). Because there is no data available on the growth cycle, population dynamics, or predatory behaviour, it is difficult to estimate the impact their introduction has had and could have on native biota. Current research, led by Dr. Tag Engstrom and Dr. Michael Marchetti from the Center for Ecosystem Research, is investigating the distribution of the softshell turtles on the Hawaiian Islands and their effect on the local ecosystem dynamics (Engstrom, 2013; Radford, 2011).
The wattle-necked softshell turtle is currently listed as endangered on the IUCN Red List due to high demand for turtle products throughout Asia, particularly within China (ATTWG, 2000; Shi et al., 2008).The market for softshell turtle meat for use in traditional Chinese food and medicine is the leading cause of the dramatic population declines. The ongoing capture and trade of the endangered species means that it is unlikely to succeed within its native habitat (Radford, 2011; Shi et al., 2008). The research by Dr. Tag Engstrom and Dr. Michael Marchetti is investigating the invasion/conservation paradox of the softshell turtle and its potential for preservation in its “new” homeland, leading the conversation for the conservation conundrum.
Ex situ conservation
Traditional methods of ex situ conservation involve the translocation or removal of part of a population from its natural habitat to a less threatened location for the preservation of genes or populations. Drawbacks associated with traditional ex situ conservation lie in the inability of the species to thrive within its new habitat due to specific environmental needs. Within the invasion/conservation paradox, the threatened species has already found a more suitable non-native habitat where it has successfully established. Instead of kicking out the intruder, perhaps the populations can be managed closely to allow their persistence.
Within the invasion/conservation paradox, there must be an assessment of risks and benefits, as with many practices of conservation ecology. Do we risk an ecosystem to save one alien species? Or do we eradicate the invader – as most methods of conservation teach – but then risk losing that species entirely? The key is understanding the full impact of the introduced species on the ecosystem it is invading. This is often easier said than done. The complexity of ecosystems and our inability to completely understand all underlying interactions and potential effects makes in difficult for us to anticipate all consequences of introduced species. As with the wattle neck soft-shelled turtle, the species has been naturalized for nearly two centuries and we still don’t know what effects, if any, it has had upon the Hawaiian ecosystem. Yet other species, such as the Monterey Cypress in New Zealand, seem to be perfectly at home within their new habitat without having serious consequences for the native flora and fauna. And then there is the Brook trout, that whilst being damaging to native fishes, is likely to persist in introduced areas due to the demand by anglers. Should this be taken as an opportunity for conservation?
Situations where the non-native species is not considered to be highly detrimental to the native biota create an interesting and new concept of ex situ conservation that could challenge the traditional perception of introduced species. This is a new concept in biology, that requires more questions to be asked, more species to be reevaluated, and more exploration into the many paradoxes that come with the responsibility of conservation.
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