近年來，作為演化網路的眾多分類中最著名的子類之一，樹子網路吸引了許多數學家與生物學家的注意。然而直到幾年前，樹子網路的精確和漸進計數仍然很困難，遑論其它問題。在本碩論中，我們將回顧以往樹子網路及其變體的一些重要結果，並添加幾個新的結果。

藉由組合學和概率論中的工具，我們實現的主要貢獻有：在單組分樹子網路下證明了最近的一個對於樹子網絡精確計數的猜想；此外，得到了第一個在均勻隨機選取樹子網路時的隨機結果；同時，還擴展了樹子網路的定義並將前人的和我們的結果推廣到這一新類；另外，也使先前對於有序樹子網路中圖案極限規律的研究更進一步，且提供了首個對一類演化網路中一般圖形的研究。

該碩論的簡短概述如下：首先在第1章中，我們給出了樹子網路、樹子網路的擴展以及有序樹子網路的定義和基本性質；然後在第2章中，我們介紹了所用的工具。其次在第3和第4章，我們分別對樹子網路及其擴展進行研究。接著在第5章，我們將以往對於有序樹子網路的研究推廣到所有高度為1和2的圖案，再給出對於任意高度圖案的推論。最後在第6章，我們總結全文。

In recent years, as one of the most prominent subclass among the many different classes of phylogenetic networks, the class of tree-child networks has attracted the attention of many mathematicians and biologists. However, until a few years ago, both exact and asymptotic counting for tree-child networks was still difficult, not to mention other problems. In this thesis, we will review the most important previous results for tree-child networks and their variants and add several new results.

Our main contributions, which are mainly proved with tools from Combinatorics and Probability Theory, are as follows. For a recent conjecture on the exact counting of tree-child
networks, we give a proof for the special case when the tree-child network is a one-component network. In addition, we prove the first stochastic results for tree-child networks which are picked uniformly at random. Also, we can extend the definition of tree-child networks and generalize previous and our results to the new class. Moreover, we have taken the previous research on limit laws of patterns in ranked tree-child network a step further and provided the
first general patterns study for a class of phylogenetic networks.

A short outline of the thesis is as follows: in Chapter 1, we give definitions and show some basic properties for tree-child networks, their extensions and ranked tree-child networks. Then, in Chapter 2, we introduce our tools. In Chapter 3 and Chapter 4, we focus on results for tree-child networks and their extensions, respectively. Next in Chapter 5, we generalize the former study on patterns of ranked tree-child networkto all patterns of height 1 and 2 and make a conjecture for patterns of any height. Finally, we finish the thesis in Chapter 6 with a conclusion.

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