Introduced species crossing with native species?

[Epiphyte]

Check this out... Carpobrotus edulis x virescens. Carpobrotus edullis is native to South Africa while Carpobrotus virescens is native to Australia. C. edullis was introduced to Australia and the two species naturally hybridize. Since the two species are compatible, I wonder how long virescens has been in Australia. Evidently birds eat the fruits of Carpobrotus species and disseminate the seeds.

Have any of you ever eaten Carpobrotus edullis? As its name suggests... the leaves are edible as well as the fruit.

What are other examples of introduced species crossing with native species?

[Rivera]

I have eaten a small quantity of wild carpobrotus edulis. I wouldn't say it made me sick, but I didn't feel great either! I didn't go back for more.

[edds]

What are other examples of introduced species crossing with native species?

For plants, Spanish bluebells are wiping out pure population's of English bluebells in the UK.

In animals,
introduced goldfish are interbreeding and wiping out pure crucian carp populations and
the ruddy duck has been removed from the UK as interbred with the vulnerable white tailed duck in Europe and would have interbred and wiped out that species.

[gave_agave]

Wild cats are threathened by interbreeding with domestic cats.

[Rivera]

Festuca idahoensis 'Siskiyou Blue,' once accepted as a pure California native, is now thought to be a wild hybrid of native CA fescue and introduced European blue fescue. It's a popular landscape plant here and is widely available at native and non-specialty nurseries.

[Paul S]

In the Canary Islands there is an increased planting of Phoenix dactylifera as an ornamental. Increasingly it is possible to see nursery stock of Phoenix canariensis (new plantings along road sides, in resorts etc) that is suckering - the dacty genes are inexorably moving in. At the moment the wild stands I've seen seem OK but it is only a matter of time.

[Gafoto]

Could probably have an entire thread on introduced trout in the west mixing with and outcompeting native species.

[gave_agave]

Could probably have an entire thread on introduced trout in the west mixing with and outcompeting native species.

Sometimes it seems the only thing fish-ecologist do is removing non-native trout (sometimes by poisoining streams and kill everything in it) and re-introduce native species.

[Epiphyte]

i love a good grave dig. i totally forgot about this thread. a few years after posting it i had the wonderful opportunity to visit john bleck's garden. it's the best mix of ornamentals and edibles, including a whole carpet of carpobrotus deliciosus. it was the 1st time i'd even heard of it. tasted like a small salty fig.

even though i'd forgotten about this thread, i haven't forgotten about the topic. i've studied it quite a bit.

not too long ago the consensus was that hybridization was rare and generally resulted in a net loss of biodiversity. now it seems like the consensus, at least among the subject matter experts, is the opposite. unfortunately most people haven't gotten the memo.

for example...scottish wildcats that are deemed inadequatly pure, due to mixing with too many domestic cats, are culled. this is incredibly counterproductive. let's say that a big domestic cat crosses with a wildcat and the result is a cat that can hunt relatively larger prey. did the domestic cat use the wildcat to fill a new niche? or did the wildcat use the domestic cat to fill a new niche? what matters is that a cat filled a new niche.

hybridization -> diversity -> adaptive radiation

cross any two aloes and maybe you don't get anything. or maybe you get something but it's sterile. these failures aren't arguments for less hybridization, they are arguments for more hybridization. because the more aloes you cross, the greater the chances of getting something that can fill a new niche.

[gave_agave]

for example...scottish wildcats that are deemed inadequatly pure, due to mixing with too many domestic cats, are culled. this is incredibly counterproductive. let's say that a big domestic cat crosses with a wildcat and the result is a cat that can hunt relatively larger prey. did the domestic cat use the wildcat to fill a new niche? or did the wildcat use the domestic cat to fill a new niche? what matters is that a cat filled a new niche.

hybridization -> diversity -> adaptive radiation

It depends...often times conservationists want to preserve populations/species/genetics. If that's the goal, than hybrid cats don't meet that goal. An animal evolved in an area to fullfill a certain niche, changing that, independently from the usual drivers, change the relationship with its niche. Do Scottisch wildcat need to be able to hunt bigger prey? There isn't really bigger prey available to them, unless they get so big they can take down roe deer and red deer (but that's very much unwanted as then they can also take down sheep).

Sometimes though that's how it goes. They save the Mauritius kestrel, whose population was down to 4 individuals. They were lizard eating raptors, and the lizards were decimated by introduced rats and cats. The species was saved with captive breeding, but in captivity they are fed mice and day old chicks. Released birds hunt mice, and do well. The species is saved, but it now has a different niche. The original genetics might have been saved, but now there are very different drivers driving gene selection. It is what it is in that case.

Overall there are many instances where most of the concepts of species we use don't apply. East coas beetles might not be able to hybridize with west coast beetles, and be seen as different species. But there might be geneflow between them because both breed with 'species' between them. Another example are the red wolves and the coy-wolves in the US. Different species or naturally existing hybrids, or hybrids evolved under human pressure?

[Rivera]

i love a good grave dig. i totally forgot about this thread.

I was surprised it was unanswered, and it seemed worthy of resurrection!

[Epiphyte]

for example...scottish wildcats that are deemed inadequatly pure, due to mixing with too many domestic cats, are culled. this is incredibly counterproductive. let's say that a big domestic cat crosses with a wildcat and the result is a cat that can hunt relatively larger prey. did the domestic cat use the wildcat to fill a new niche? or did the wildcat use the domestic cat to fill a new niche? what matters is that a cat filled a new niche.

hybridization -> diversity -> adaptive radiation

It depends...often times conservationists want to preserve populations/species/genetics. If that's the goal, than hybrid cats don't meet that goal. An animal evolved in an area to fullfill a certain niche, changing that, independently from the usual drivers, change the relationship with its niche. Do Scottisch wildcat need to be able to hunt bigger prey? There isn't really bigger prey available to them, unless they get so big they can take down roe deer and red deer (but that's very much unwanted as then they can also take down sheep).

i just thoroughly enjoyed this video of a cat catching a squirrel. do we need cats, wild or otherwise, to be able to hunt squirrels? yes, very yes. squirrels are the worst.

all deer range in size from newborns to fully mature adults. plus the uk has a continuum of bird sizes. for every size prey there should be wild cats and/or canines capable of hunting them.

not too long ago there was a viral video of a local toddler in her front yard being dragged off by a coyote.

An individual human life has no equivalent. But that is not to say that nothing can be ranked with, let alone outrank, a human life. The French government knows that each year several drivers lose their lives because of the beautiful roadside avenues of trees, yet they do not cut them down. Even aesthetic pleasure is (rightly) allowed to outrank a certain number of human lives. It is easy here to move imperceptibly from Kant to cant. - James Griffin, Well-being

Sometimes though that's how it goes. They save the Mauritius kestrel, whose population was down to 4 individuals. They were lizard eating raptors, and the lizards were decimated by introduced rats and cats. The species was saved with captive breeding, but in captivity they are fed mice and day old chicks. Released birds hunt mice, and do well. The species is saved, but it now has a different niche. The original genetics might have been saved, but now there are very different drivers driving gene selection. It is what it is in that case.

yeah if the focus had been on "saving" early humans we wouldn't be here. we'd still be in africa hunting and gathering.

[gave_agave]

That's a very American view of wildlife management (and I'm not saying that's good or bad). Domestic cats kills billions of native wildlife every year, and are a big threat to native wildlife in many areas. Especially in countries where they aren't native (like Australia and New Zealand). There are many more predators around than domestic cats, coyotes and wolves. There are shrews, various species of different sizes of mustelids and viverrids. The pressure on birds is huge. They suffer from a sharp decline in food (there are HUGE reductions in insects, mostly from agricultural practices), climate change (decoupling of timing between hatching of young and peaking numbers of prey to feed their young), non-native predators (like cats), and then there is hunting (well regulated in the US, but a problem around the Mediterranean and Middle-East mostly). Taking away the pressure from cats on birds is a much easier step then changing agricultural practice on a large scale (moving later and more infrequently, bigger strips of land planted with native flowering plants instead of food crops), much less use of pesticides and herbicides, leaving land bare to recover more frequently etc.
Why single out the one incident of a coyote with a child, but not all the damage and people getting injured in car crashes with deer? There are a few hunderd casualties and thousands of people getting injured. In many states in the US the management goal for deer is based on maximum hunting opportunities, ie more deer. This comes with controlling predator population (as they're a competitor for hunters), and all the narratives supporting that. With more natural predator number there would maybe be a few dozen more cases of incidents between people and predators, but there would also likely be tens of thousands fewer collisions between deer and cars, saving millions in damages, and hundreds or thousands of injuries. But it would also mean much fewer hunting opportunities. Ultimately, in those cases, it comes down to what society wants (how many hunting opportunities do they want), and how much do they tolerate (human-wildlife incidents like predator attacks, traffic collisions, and also hunting accidents).

[Stan]

Even going native is bad some say. Yards near greenbelts might be hybridize with local flora..bad for the genes. Also people who plant natives might not be the best gardeners and their sick or infected native could jump to wild plants. Natives are perfectly safe from my Aloes and Mexican cloud forest plants.

[Epiphyte]

gave_agave, let's put it in terms of team agave versus team aloe. all else being equal, if team agave's focus is on "saving" the "purity" of each agave species, while team aloe's focus is on using hybridization to put aloes in as many new niches as possible, then team aloe will beat team agave hands down in the evolutionary sense.

right now i'm pretty excited about "my" aloe bakeri hybrids. technically the hummingbirds (or bees?) deserve credit for them. i currently have bakeri x arborescens (i guess) blooming right next to bakeri x striata (i guess). the hummingbirds go back in forth between them every day. we don't necessarily consider the consequences of creating any cool new combinations, but success always has some detrimental consequences...

But have you ever asked yourselves sufficiently how much the erection of every ideal on earth has cost? How much reality has had to be misunderstood and slandered, how many lies have had to be sanctified, how many consciences disturbed, how much "God" sacrificed every time? If a temple is to be erected a temple must be destroyed: that is the law – let anyone who can show me a case in which it is not fulfilled! – Friedrich Nietzsche, On the Genealogy of Morality

any cool new bakeri hybrids will proliferate and take up space in gardens that could have been used for agaves and countless other plants.

naturally i can't worry about personally proliferating every form of life, but whether somebody loves agaves, weird fruits, scottish wildcats, trouts or falcons, they should focus on hybridizing them as much as possible. doing the opposite, trying to keep them pure, is entirely counterproductive.

[edds]

gave_agave, let's put it in terms of team agave versus team aloe. all else being equal, if team agave's focus is on "saving" the "purity" of each agave species, while team aloe's focus is on using hybridization to put aloes in as many new niches as possible, then team aloe will beat team agave hands down in the evolutionary sense.

That is a misunderstanding. Many hybrids will have limited evolutionary lifespans as they are not as well adapted to the niche either parent species was. They may proliferate in the short term (a few thousand years) but not in the long term, whereas many 'pure' species will survive.

Even worse, some will show hybrid vigour in the first generation then reduced fertility over the following generations.

The hybrids can also impact other species success in an ecosystem having knock on effects.

English Bluebells are a good example as the hybrid bluebells grow larger. In a pristine environment that is nutrient limited they are less successful than the native form but they are so fertile they cross anyway making the whole population less successful. Many generations of selection pressure may move the population back to close to the native form but so many of our habitats are degraded that the pool of hybrid genes will live on.
These larger hybrids also can swamp other emerging flora with their larger leaves reducing the mix of other plants in a woodland impacting on the flowering of those species and the nectar and pollen availability.

Evolution specialises for a reason and the refinement of adaptation to niches. When there is habitat disturbance, generalists proliferate but with stable habitat's the specialists come to dominate again.

Does this matter in the long term - no, new species will evolve. But in the short term (our, our children and grandchildren's lives) it will leave our world a much poorer place for our lack of thought and consideration of nature.

[gave_agave]

Hybridisation sometimes can lead to new species, but definitely isn't the only way species evolve, or how 'genes' can take up new niches. Most species don't originate from hybridisation, but from isolation from others, and following their own evolutionary path. If their path doesn't work, they go extinct, if it works, they persist, and might evolve in yet other species. Sometimes 2 species come together, their offspring is fertile, and they get isolated again, and form a new species. Sometimes geneflow persists among populations of what we consider different species. This geneflow can be constant, erratic, common, rare, stable, increasing or decreasing. Pretty much any scenario you can think of, will exist somewhere. None of them are 'better' or 'worse', it's just that some work for some in some places, while others work for others in other places.

And even stable conditions, which edds pointed out could lead to dominance of a few specialists, but if it lasts long enough, and if circumstances allow, can lead to environments with incredible biodiversity, as even the tiniest niche (and tiniest not meaning in area), might have a specialist. That's what we see in rainforests for example. Very stable environments, where every niche is filled by a different species.

And to what extent should we see interference by humans as interference? For example, European wall lizards are establishing populations in the UK and are considered non-native and sometimes classified as invasive as they can't naturally reach the UK. But, what if a lizards just uses opportunities presented to them, by creeping into some clothes in France, and being transported by people in their car to the UK, then slither out of the clothes and into a garden and live happily? How much different is that from a lizard being picked up by a predatory bird and then dropped miles further when the bird gets attacked by another bird who wants to steal the lizard? In both cases the lizard was transported to a new place not by its own means, but it 'used' an opportunity presented to it? Presenting yourself to people so they take care of you, or move you (without killing) could also be an evolutionary trait. The lizard might be a poor example, but that certainly plays a role for plants. If you're more attractive to bees or birds you used to be more successful, but now you might be even more successful in spreading your genes, as a plant, if you're attractive to people.

The whole evolutionary process and speciation is very fascinating!

[Epiphyte]

gave_agave, let's put it in terms of team agave versus team aloe. all else being equal, if team agave's focus is on "saving" the "purity" of each agave species, while team aloe's focus is on using hybridization to put aloes in as many new niches as possible, then team aloe will beat team agave hands down in the evolutionary sense.

That is a misunderstanding. Many hybrids will have limited evolutionary lifespans as they are not as well adapted to the niche either parent species was. They may proliferate in the short term (a few thousand years) but not in the long term, whereas many 'pure' species will survive.

hybridization is a hedge. the point of hedging is to increase the chances of success in the face of the unknown.

here in socal it's been the longest winter that i can remember. the only plants in my garden that are happy are the aeoniums. they essentially help to hedge my bets against the cold. an even bigger hedge against the cold would be if i bought a green gage plum. i've never tasted it but i remember my grandfather saying it was easily the best plum he ever tried. if future winters are like this one then a green gage plum would get enough chill hours to produce fruit.

if i had a crystal ball then hedging would be pointless. sadly i don't have a crystal ball. nobody does. the future is always uncertain.

the english bluebells would be fine if the climate didn't change much. but if the climate changes drastically? let's say that the weather quickly becomes hotter and drier. the english bluebell on its own wouldn't be able to adapt fast enough and then it would be game over. but it would be a different story for some of the english bluebells that had been lucky enough to cross with the spanish bluebells.

even if the climate doesn't change drastically, the english bluebell wants to colonize areas with different climates...

The open road still softly calls, like a nearly forgotten song of childhood. We invest far-off places with a certain romance. This appeal, I suspect, has been meticulously crafted by natural selection as an essential element in our survival. Long summers, mild winters, rich harvests, plentiful game—none of them lasts forever. It is beyond our powers to predict the future. Catastrophic events have a way of sneaking up on us, of catching us unaware. Your own life, or your band's, or even your species' might be owed to a restless few—drawn, by a craving they can hardly articulate or understand, to undiscovered lands and new worlds. - Carl Sagan, Wanderers

colonization can be facilitated by hybridization.

[gave_agave]

even if the climate doesn't change drastically, the english bluebell wants to colonize areas with different climates...

However, colonization potential is heavily impacted by people, as many areas are now occupied. Bluebells can't colonize meadows, agricultural fields, build up areas etc. For animals there are a lot of structures obstructing their potential paths to colonize other areas.
In Southern Africa they, quite successfully, are mimicking dispersal and colonization of cheetahs and African wild dogs with a metapopulation management program, and it raises the question if we maybe shouldn't be doing more of that. We know species ranges change with changing climate, we also know that for many species we are the cause that they won't be able to shift their range, so should we try to eliminate our impact in that respect?

[edds]

hybridization is a hedge. the point of hedging is to increase the chances of success in the face of the unknown.

I feel like I'm repeating my earlier post here but this is often not the case. Hybridisation can lead to less evolutionarily robust populations, not more robust ones.

the english bluebells would be fine if the climate didn't change much. but if the climate changes drastically? let's say that the weather quickly becomes hotter and drier. the english bluebell on its own wouldn't be able to adapt fast enough and then it would be game over. but it would be a different story for some of the english bluebells that had been lucky enough to cross with the spanish bluebells.

The introduction of Spanish Bluebell genes and plants that are larger but combine English Bluebell genes may actually make them less well adapted to either the current climate or future ones. The UK climate won't become Spain!

It may also make them less reproductively successful than either parent species. This is one mechanism by which natural hybrid swarms at the overlaps in range of two species often don't replace either parent species.


Much of your comments seem to be conflating short term survival of individuals with the health and longevity of entire species or populations. What you see in one or two generations of a population may bear no correlation with the longer term success of that group over an evolutionary significant period.

[Epiphyte]

Most species don't originate from hybridisation, but from isolation from others, and following their own evolutionary path.

is this true? i'm not quite sure...

In the mid-20th century, Edgar Anderson was the greatest proponent of the importance of hybridization in evolution (Anderson, 1949; Anderson & Stebbins, 1954), which led to light-hearted ridicule by some colleagues. As Warren H. Wagner (relayed by Michael Arnold, pers. comm.) once said, ‘We used to make fun of Edgar Anderson by saying that he was finding hybrids under every bush. Then we realized that even the bushes were hybrids’. With genomic tools, we are beginning to understand that the evolutionary importance of hybridization may even exceed Anderson’s expectation. - abbot et al, hybridization and speciation

even if the climate doesn't change drastically, the english bluebell wants to colonize areas with different climates...

However, colonization potential is heavily impacted by people, as many areas are now occupied. Bluebells can't colonize meadows, agricultural fields, build up areas etc. For animals there are a lot of structures obstructing their potential paths to colonize other areas.

This kinda relates to anderson's 1948 paper... hybridization of the habitat.

nearly a decade ago i proposed in an orchid forum that the florida ghost orchid (dendrophylax lindenii) be crossed with the more drought tolerant dendrophylax funalis (from jamaica). hybridization between these two species would facilitate their colonization of habitats outside the everglades... such as roadside trees, garden trees, orchards and so on. my idea met with a "bit" of resistance.

[Epiphyte]

hybridization is a hedge. the point of hedging is to increase the chances of success in the face of the unknown.

I feel like I'm repeating my earlier post here but this is often not the case. Hybridisation can lead to less evolutionarily robust populations, not more robust ones.

grizzilies and polar bears have been known to hybridize. if, as a result of hybridization, polar bears all became brownish then they wouldn't be as camouflaged so they would be less fit. except how likely is it that polar bears would all become brownish? how did polar bears become white in the 1st place? the lighter colored individuals were better camouflaged, so they were more successful at hunting than the darker colored individuals.

hybridization doesn't facilitate the proliferation of darker colored individuals in lighter colored environments. hybridization doesn't facilitate the proliferation of less fit individuals. what hybridization does do is facilitate faster adaptation to rapidly changing environments. if the arctic rapidly becomes a darker environment, then hybridization would facilitate the faster proliferation of darker bears.

according to a quick google search, by 2050 the temperature will be 2.7° degrees fahrenheit warmer. is this enough to turn the uk into spain? maybe not, but it's certainly a relatively rapid shift in that direction.

[gave_agave]

The split between polar bears and grizzlies is actually relatively recent, and happened because of isolation from each other. Now grizzlies push further north again due to warming, they're starting to mix again. We don't know what the effects of that will be.
But 'isolation' is also a relative term, it doesn't mean that there totally wasn't any exchange of genes ('hybridisation' - just like most people have some of their genetics from Neanderthales).
Sometimes a colour change is an instant thing which sticks and spread, involving just one gene, sometimes it's a gradual thing involving multiple genes. Like I said before, there are many ways, you think of one, there probably is an example of it in the real world. Hybridisation might help to adjust to new environments, but what's even better to adjust to new environments is heterozygosity. The higher the heterozygosity in a population, the greater the potential to adapt. Small population cans, quite rapidly, lead to a great reducity in heterozygosity (due to inbreeding), and thus an increase in homozygosity. Gaining heterozygosity, takes a lot longer than losing it, it isn't a simple process of some errors happening by chance by DNA multiplication and that leading to functional heterozygosity. Many of those errors are detrimental, or have no effect, and the ones who might be useful, are completely dependent on chance for sticking in the population until there is a selection pressure for it.