[MUSIC] For practical reasons, I will use one particular group as illustration, the Passerine birds, or song birds. I will not dwell with the techniques of data handling and hypothesis testing, but mainly use large scale distributional patterns to illustrate historical/ evolutionary processes. The passerine birds are not necessarily more interesting than other groups of organisms but or provide a more true picture than the other groups. But I use this group because no other groups are known so well in such detail. The color page right in front of me here that I'm painting on shows some species of passerines that still are not formally described, they have no name. So, there are still some birds of this kind that still have no formal name. But, we assume overall that we know all the passerine birds of the world. And at least much better than for other groups. The knowledge gaps would be much greater if we choose any other group. So, in general we may say today that we know the passerine birds of the world, and we know where they are distributed. And for most of the species, we know a good deal about their life history and their environmental requirements. Now this allows us to undertake some global scale analysis with a confidence that is not possible for other organismal groups. With more than 6,000 species of passerine birds or nearly two-thirds of all birds, this group is a suitable-sized group for analysis. They are all over world and have undergone a tremendous adaptive radiation as you see on the illustration here. There is a very great variation. Most of them are small, but the lyre bird in the middle is about one kilo. And there are various specializations among the others. You can see some on the painting. Some with thin bills for nectar feeding. Others that are fly catching, flying out in the air like the swallows, and flycatchers. Others that are seed eaters, and granivores. In other words, they are everywhere, and they are specialized to take all the kinds of resources that you find around in the terrestrial environment. So, now I will explain what kind of data we are using for this analysis. So here is a lot of data files with different data sets. So I just open here. Distributional data for all passerine birds. Here they are we can, the red is of course the most species rich area and the pale blue where there are very few species at all, and we can zoom into an area for instance, here down in Australia, and to see details. And then we can go in to the data layers and look at where the different species are. So, in Australia and New Zealand New Guinea. So, all the species are being entered into one degree grid cells here and then we compile it all. And then these data can be exported into various statistical programs and then correlated with Earth data, with ecological data for each of the grid cells or it can be coupled together with phylogenies. So why are the passerines so successful and widespread? Well, there are many factors. First of all small birds with high metabolic rate also evolve faster and have high speciation rates. New species evolve rapidly and they don't require large territories and large food resources. But I will point out also another much overlooked factor. The most ancient bird groups have so-called precocial young. We take some of them here: partridge chicks. They hatch, fully developed after one half hour, one hour after hatching, they can already start moving around, and they find their own food. This seems to be a very smart adaptation, especially from the parents' point of view, that they can fend for themselves. But also it requires a lot of energy investment in the egg, to produce such young and actually it restricts the birds quite much. They feed on items that even a totally inexperienced naive chick can find for itself. So actually it restricts distribution of such birds and their success. Passerine birds are actually very much more advanced than this. Their young - chick of a crow here - they hatch blind and naked while this is a little more grown but when they are newly hatched it is actually like a larva where only the gaping reflex - like this, and the guts and liver is fully developed. So the adults have to put food into it and a lot of work, but, on the other hand, it also gives some opportunities that they can place the young in smart nests as we see here in an oriole nest that is suspended between twigs high up in a tree in a safe place. All these adaptations allow the adults to move everywhere to catch food for later on. So they can go up in the treetops everywhere, in the vegetation. Up in the air, to catch food, it opens the whole world for new exploration and feeding excursions. So this is a reason why these birds can actually spread into all kinds of terrestrial environment around the world. The consequence of this is that passerine birds could distribute themselves all over the world in a way that appears to correspond quite well with other terrestrial biodiversity. We see on the slide here the species richness of passerine birds all over the world. The red colors are the highest diversity and the dark blue is where there are very few species up in the Arctic and in the desert regions. This pattern corresponds quite well to a pattern for other large organismal groups. Of course this does not reflect a biodiversity gradient in the oceans, which is a very different thing that I will not talk about now. So, how do we explain such pattern? The general latitudinal diversity gradient with much the red colors. Higher richness in the tropics and the patchiness that we can also observe. Look, for instance, on the map on the Central Congo Basin. That is actually, that's rain forest but it is not species rich. There are many local hot spots and there are also cool spots. There are, of course, many contributions and factors and if we look at a globe instead of a flat map, we would also see that some of it could actually simply be an effect of area. There is a very large land area around the equator - available area is one contributing factor. So to further analyze the underlying causes, one actually has to look for deviations from statistical null models that take into account a number of factors like the extent and shape of the various land areas. I will then demonstrate some of the complications of such analyses just by a closer look at Africa, based on a study published in Science a decade ago by Walter Jetz at Yale University, and my colleague Carsten Rahbek here in Copenhagen. And so, you see on the maps here, the darkest red color is where we have the highest number of species. This is based on all together 1,600 resident African bird species. The maps on the left side here are divided in quartiles, that is, groups of 25% of the species. The lower left is the 25% of the species that are most widespread. They actually contribute 70.5% of all the data points in the all species maps and we can see that they actually produce almost the same diversity pattern. The quartile with the species with the smallest distributions, they only contribute 1.5% that is in the upper left and we can see that they are very concentrated just in Africa's mountain areas. Widespread and locally distributed species show very different diversity patterns. But it is the latter, those with the small ranges which generally comprise the rarest of the species, those of greatest environmental concern, they actually contribute very little to the overall pattern. Now we need to look at what this reflects while this pattern, it seemed to be a very universal one. We find that all over the world for all different groups, and for all the continents the majority of species are very widespread. They simply survive by moving around in response to changing environmental conditions, while other species are specialized to a local environment. They live only in some certain small areas. So, let us look at the environmental conditions that best explain these patterns. Still on this analysis of the African bird distributions, if we look at the graphs here, this shows which factors best explain the different patterns. Nearly 70% of the distributions of widespread species can actually be explained by one single factor, namely the net primary reproduction, which is a consequence of temperature and availability of water. So this species have apparently managed to distribute themselves across the world in a way that corresponds very well to the photosynthesis and availability of food. Landscape complexity may explain a little more. So, actually we have a quite complete explanation of the path of the distribution of widespread species. This is in strong context to the species with very small distribution. Where only 7% of the variation can be explained from the primary production. 40% can be explained from topographic range. But this still leaves a lot of unexplained variation. I will come back to this later. [MUSIC]
