>> Hello students. This is plants and animals of southern California. As you're walking through the mountains around here, then you'll see that there's different vegetation depending on the aspect, that is, the direction that the hillside is pointing. So, we might be on a hillside where it's south-facing. And on that hillside we'd probably be surrounded by things like purple sage and maybe some Malosma laurina, laurel sumac. So, and it would probably be mostly coastal sage scrub, right? Which is a vegetation type. And these vegetation types tend to kind of smear into one another and not be very categorical. Then we could be looking across a little valley, a little riparian area onto a north-facing slope. So we're at a south-facing slope and we're looking at a north-facing slope. And that north-facing slope then might even have big cone Douglas fir on it. And then it would be dominated by sclerophyllous things, maybe some coast live oak. And probably a very dense vegetation. And then if we kind of walked over the hill, then we could be on an east-facing slope. And on that east-facing slope, if we were at Towsley Canyon, it would be dominated by California flowering ash. The different species of plants would occupy different parts of the landscape. And aspect, or the direction in relation to the sun, or compass direction, would be a big component of what was determining which plants dominated where on that landscape. Another one would be the relation to water drainages. So, of course, in the riparian zones, there would be different plants than in places that are just little rivulets, seasonal rivulets. And that would be a little bit different than places that were the slopes of the hills or the shoulders of the hills or the ridge tops. So, those things, the topography and the aspect would determine which different plants are living in which different places. That business of where plants grow in relation to topography and aspect, that's because of a little bit complicated dynamics involved in the niche. So there's the physical environment of how much water is at that place and how much sun that place gets. And that would maybe define what we might think of as the fundamental niche of the species. So different species would have different fundamental niches. Some of them would require more water. Some of them require less water. Some of them are more tolerant of sun. Some of them are less tolerant of a lot of sun. But then that fundamental niche is further modified by the relationships with the other plants. So, it's quite possible that purple sage would love growing on the east side of the mountain, and the reason why it doesn't grow on the east side of the mountain is because it's in competition with other plants that can grow on the east side of the mountain, like the California flowering ash. California flowering ash dominates on the east side. And maybe it then shades out or sort of out-competes some of the purple sage. And that would be because of the realized niche, the niche that's determined after you consider all the competitive interactions, and also possibly facilitative interactions with the other plants. So all of this sort of goes into thinking about the physiological ecology of those individual plants as they are spread out on the landscape. But, we should consider not just the physiological ecology of individuals, but also what allows populations to exist in a larger area or for a larger period of time. So it's quite possible that in some place around Towsley Canyon we could have bigleafed maple. There might be a place that it would be physically fine for bigleaf maple to grow. But there's a problem. How do you get a bigleaf maple seed there? And then even if you got a bigleaf maple seed there and it grew and it made a plant, what other bigleaf maple would it mate with? So in order for a population to be maintained, it not only has to have the appropriate niche, but it also has to have a means of dispersing to that place. And then it has to maintain a population so that it's not just the life of that individual that's sustained, but the whole population is sustained over multiple generations, which requires, often, being connected to other individuals of the same species. So then let's make a little like logic tree in our mind. First, there's the distinction between the ability to disperse to a spot. And then whether it can live in that spot. And so dispersal is this really important thing that contributes to which plants live where on the earth, right? Like there were a whole bunch of plants that could live in California but never could get to California that lived in the Mediterranean basin. And then when people showed up from Europe, they brought with them a lot of seeds, just you know, inadvertently. Like seeds that were associated with their livestock or whatever. Those seeds got carried over here and then they spread like mad in California because they had appropriate niches. So dispersal is a big part of what determines which species live in a region. And then as you go to smaller and smaller spatial scales, dispersal is easier and easier. And so the populations of those species would be less and less limited by dispersal. In the type of landscape that you can walk around in a day, I would assume that all of the plants that you see could disperse anywhere in that landscape, right? Because it's a pretty small place. Now, there's various dispersal means that different plants have. So, California flowering ash, it has little propellers on the seeds. And that might get it a fair ways. But, maybe not too far. And then something like redberry. Those, of course, are dispersed by birds. And lots and lots of the chaparral species, the shrub species, are dispersed by birds or by maybe by mammals. Like arctostaphylos is probably dispersed by mammals more. And I think probably Prunus ilicifolia is dispersed by mammals more than by birds. And then, there's other plants that make burrs on the outside of their seeds that stick to fur, or they would stick to your socks. And so they get around on top of animals rather than through the guts of animals. And then some things just have really tiny seeds. And so that also facilitates them blowing around and getting from place to place. And if they have tiny seeds and the seeds last for years and years, then that also means that they could get farther and farther. So there's all these dispersal mechanisms that different organizations have. Oh, another one is sort of like the things on dandelions. They have a little parachute. So there's lots of plants that have little parachutes that will catch in the wind and blow. So, we might consider the assembly of a community as being determined partially be dispersal and then partially by the ability of individuals first to cope with the physical environment and then to cope with competitors and facilitators. And then lastly, to be able to reproduce with other individuals of their kind. In other words, in order to maintain a population. And then we also need to think about all of that in terms of the spatial scale. So a local little landscape that you could walk around is kind of different than the region of Southern California, which is different than you know, like western North America or all these kind of global issues that we're talking about with floras of different continents. And along with spatial scale also goes temporal scale. So I think we think a lot about how a community is assembled after a fire where it just kind of -- the fire kind of burns everything down to the ground. And then we think about well right after the fire and after the first rains after the fire, that stimulates a whole bunch of herbaceous wildflowers that are annuals, fire followers, to germinate and grow. And you have this great spectacular wildflower display. And then in a few years after that, you might have things like deer weed and bush poppy. And then eventually a dense cover of shrubs comes back. So that's the succession right after a fire at the landscape scale. And really, every plant in southern California, in middle and southern California is a plant that has some mechanism or other that allows it to deal with recovery after a fire because any species that didn't would be, I don't know -- well, at least it would be relegated to small little places that almost never burn, like maybe some riparian spots or something. So either they're able to disperse in really well or they've got a seed bank or they can re-sprout or something. And so even if you understood all of that, all that sort of dynamics that happens after a fire at a small spatial scale, and on the temporal scale of every few decades, then those wouldn't necessarily be the same things that would explain the dynamics and assembly of the southern California flora on a scale of tens of thousands of years or millions of years, right? So that would -- you have to kind of think about other aspects of the biology of the organisms that determine that. And one of those aspects would be how much can they disperse in from other places. So that's all that I had to say about that.