**7. Outlook**

*Birds - Challenges and Opportunities for Business, Conservation and Research*

down, it is probably only a matter of time, until we will get there.

which allowed gene flow among island taxa.

differences in vocalization [33–37].

field guides.

**6. Phylogeography**

Thus a birder, who started his career 40 years ago will sometimes no longer recognize the Latin names of a species and their order of arrangement in modern

All these efforts have expanded the world checklist of birds. The IOC World Bird List 11.1 [27] actually (2021) comprises **10,806** extant species (and **158** extinct species) organized in **40** Orders, **252** Families and **2,353** Genera. **19,990** subspecies, their ranges and authors are also included. The number so of new bird species is increasing continuously. It has been speculated that we will end up with more than 18000 bird species, when all of them have been sequenced and re-classified [28].

Another area of interest is the distribution and evolution of a species over time and space. This is the realm of phylogeography [15]. In order to use DNA for such analyses, we require highly informative DNA and methods with a high degree of resolution. Although variable mtDNA is useful in many instances, a better resolution can be obtained from the analysis of microsatellite markers. Increasingly, partial (RADSeq) and complete genome analyses from High-throughput sequencing are also used to study phylogeography because we can obtain information of millions of single nucleotide polymorphisms (SNPs). In case of human evolution, such data could trace human migrations over time and ancient hybridizations with Neanderthals and Denisovans in fascinating details [3]. It will take some time, until we will have similar data for any species of birds. But, as the costs for NGS come

We have analyzed the phylogeography of several birds and reptile species on oceanic islands (Macaronesia), in the Amazon region and in Eurasia. The pattern, which we discovered, differed substantially between regions. Although the Macaronesian islands (including Canary Islands, and Madeira and Azores) are sometime not far from each other, the local bird populations are resident and do not exchange between islands [29, 30]. All these oceanic islands are of volcanic origin and between 20 to 1 million years old. They are known for their richness of endemic fauna and flora.

When we studied the variation of mitochondrial DNA sequences of birds from different Macaronesian islands, we discovered, that many of them had specific and unique island haplotypes, suggesting that gene flow between islands is very low or not existing [29, 30]. As a consequence, some of the islands species obtained species rank, such as *Phyllocopus canariensis*. In *Fringilla coelebs, Cyanistes caeruleus, Erythacus rubecula, Regulus regulus, Sylvia melanocephala*, and others we could define new island specific subspecies (see references in [29, 30]). A similar diversification can be seen on the Island archipelago of the Wallace zone in Australasia [31]. However, if we look at bird population on the Aegean Islands in Greece or Turkey (except for Cyprus), little or no differentiation can be seen [32]. The Aegean islands have been connected with each other during the last few million years,

We also studied some bird taxa in the Amazon region and to our surprise found a strong degree of phylogeographic patterning, which correlated with the large river systems in the area. As a result, a number of morphologically similar species could be split into new taxa mostly on account of DNA data, sometimes also because of

To our surprise, we found some genetic variation in Eurasian bird species, but could often not discover a robust phylogeographic pattern. Examples are: *Lanius collurio, Merops apiaster, Upupa epops, Dendrocopus major, Tyto alba, Athene noctua, Falco peregrinus* or *Acrocephalus palustris* [38–43]. The apparent reason for this

**16**

As a consequence of new DNA analyses and the use of cladistics, the number of extent bird species is growing from year to year. We presently recognize well over10,806 bird species; some estimates assume even more than 18,000 bird taxa if subspecies will attain species level [28]. Even if we see very good progress over recent years, it will certainly take some time until the final "Avian Tree of Life" will be published, in which the phylogenetic position and history for each of the avian species is reconstructed. A Tree of Life, will enable a better understanding of avian evolution in general, of systematics but also of the evolution of traits and adaptations.

## **Acknowledgements**

I would like to thank my students and collaborators over 30 years for their continuous support. Our work was funded by grants of German Science Foundation (DFG), German Academic Exchange Service (DAAD), COST, Chinese Scholarship Council (CSC), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), National Council of Science and Technology (CONACYT), Science and Technology Development Fund (STDF) and German Ornithologist Society (DO-G.
