Papua New Guinea, of course.
http://www.atlasandboots.com/worlds-most-diverse-country/
1 Papua New Guinea 1.000
2 Tanzania 0.953
3 Democratic Republic of Congo 0.933
4 Uganda 0.930
5 Liberia 0.899
6 Cameroon 0.887
7 Togo 0.883
8 South Africa 0.880
9 Congo 0.878
10 Madagascar 0.861
11 Gabon 0.857
12 Kenya 0.852
13 Ghana 0.846
14 Malawi 0.829
15 Guinea-Bissau 0.818
16 Somalia 0.812
17 India 0.811
18 Nigeria 0.805
19 Yugoslavia (1943-1992) 0.801
20 Central African Republic 0.791
21 Ivory Coast 0.784
22 Lebanon 0.780
23 Chad 0.772
24 Indonesia 0.766
25 Mozambique 0.765
26 Gambia 0.764
27 Sierra Leone 0.764
28 Ethiopia 0.760
29 Angola 0.756
30 Mali 0.754
31 Afghanistan 0.751
32 Bolivia 0.743
33 United Arab Emirates 0.737
34 Senegal 0.727
35 Zambia 0.726
36 Namibia 0.724
37 USSR (1922-1991) 0.711
38 Sudan (1955-2011) 0.708
39 Kuwait 0.708
40 Burkina Faso 0.704
41 Bosnia and Herzegovina 0.681
42 Kyrgyzstan 0.679
43 Nepal 0.677
44 Iran 0.669
45 Guinea 0.669
46 Kazakhstan 0.664
47 Colombia 0.656
48 Ecuador 0.655
49 Eritrea 0.647
50 Trinidad and Tobago 0.647
51 Peru 0.638
52 Niger 0.637
53 Mauritius 0.632
54 Mauritania 0.625
55 Benin 0.622
56 Guyana 0.620
57 Djibouti 0.606
58 Bhutan 0.605
59 Malaysia 0.596
60 Canada 0.596
61 Latvia 0.585
62 Syria 0.581
63 Switzerland 0.575
64 Yugoslavia (1918-1943) 0.575
65 Belgium 0.567
66 Fiji 0.566
67 Saudi Arabia 0.553
68 Bahrain 0.551
69 Iraq 0.549
70 Brazil 0.549
71 Mexico 0.542
72 Macedonia 0.535
73 Pakistan 0.532
74 Israel 0.526
75 Burma 0.522
76 Tajikistan 0.513
77 Estonia 0.511
78 Moldova 0.510
79 Jordan 0.509
80 Panama 0.507
81 Czechoslovakia (1918-1992) 0.505
82 Spain 0.502
83 Chile 0.497
84 Guatemala 0.493
85 United States 0.491
86 Georgia 0.490
87 Uzbekistan 0.485
88 Venezuela 0.483
89 Laos 0.481
90 Morocco 0.479
91 Oman 0.439
92 Thailand 0.431
93 Sri Lanka 0.428
94 Ukraine 0.419
95 Nicaragua 0.402
96 Turkmenistan 0.392
97 Singapore 0.388
98 Dominican Republic 0.387
99 Croatia 0.375
100 Belarus 0.372
101 Zimbabwe 0.366
102 New Zealand 0.363
103 Cyprus 0.359
104 Botswana 0.351
105 Lithuania 0.338
106 Russia 0.333
107 Slovakia 0.332
108 Burundi 0.328
109 United Kingdom 0.324
110 Czech Republic 0.322
111 Algeria 0.320
112 Romania 0.300
113 Turkey 0.299
114 Bulgaria 0.299
115 Swaziland 0.280
116 Taiwan 0.274
117 France 0.272
118 Mongolia 0.272
119 Lesotho 0.255
120 Argentina 0.255
121 Costa Rica 0.238
122 Vietnam 0.233
123 Slovenia 0.231
124 Bangladesh 0.223
125 Uruguay 0.218
126 Cuba 0.213
127 El Salvador 0.198
128 Sweden 0.189
129 Azerbaijan 0.188
130 Hungary 0.186
131 Cambodia 0.186
132 Honduras 0.185
133 Rwanda 0.180
134 Ireland 0.171
135 Jamaica 0.166
136 Egypt 0.164
137 Philippines 0.161
138 China 0.154
139 Libya 0.151
140 Australia 0.149
141 Armenia 0.134
142 Finland 0.132
143 Paraguay 0.132
144 Denmark 0.128
145 Austria 0.126
146 Norway 0.098
147 Albania 0.097
148 Germany 0.095
149 Haiti 0.095
150 Yemen 0.078
151 Netherlands 0.077
152 Greece 0.059
153 Poland 0.047
154 Portugal 0.040
155 Italy 0.040
156 Tunisia 0.039
157 Japan 0.012
158 South Korea 0.004
159 North Korea 0.002
pretty interesting list.
http://www.atlasandboots.com/worlds-most-diverse-country/
1 Papua New Guinea 1.000
2 Tanzania 0.953
3 Democratic Republic of Congo 0.933
4 Uganda 0.930
5 Liberia 0.899
6 Cameroon 0.887
7 Togo 0.883
8 South Africa 0.880
9 Congo 0.878
10 Madagascar 0.861
11 Gabon 0.857
12 Kenya 0.852
13 Ghana 0.846
14 Malawi 0.829
15 Guinea-Bissau 0.818
16 Somalia 0.812
17 India 0.811
18 Nigeria 0.805
19 Yugoslavia (1943-1992) 0.801
20 Central African Republic 0.791
21 Ivory Coast 0.784
22 Lebanon 0.780
23 Chad 0.772
24 Indonesia 0.766
25 Mozambique 0.765
26 Gambia 0.764
27 Sierra Leone 0.764
28 Ethiopia 0.760
29 Angola 0.756
30 Mali 0.754
31 Afghanistan 0.751
32 Bolivia 0.743
33 United Arab Emirates 0.737
34 Senegal 0.727
35 Zambia 0.726
36 Namibia 0.724
37 USSR (1922-1991) 0.711
38 Sudan (1955-2011) 0.708
39 Kuwait 0.708
40 Burkina Faso 0.704
41 Bosnia and Herzegovina 0.681
42 Kyrgyzstan 0.679
43 Nepal 0.677
44 Iran 0.669
45 Guinea 0.669
46 Kazakhstan 0.664
47 Colombia 0.656
48 Ecuador 0.655
49 Eritrea 0.647
50 Trinidad and Tobago 0.647
51 Peru 0.638
52 Niger 0.637
53 Mauritius 0.632
54 Mauritania 0.625
55 Benin 0.622
56 Guyana 0.620
57 Djibouti 0.606
58 Bhutan 0.605
59 Malaysia 0.596
60 Canada 0.596
61 Latvia 0.585
62 Syria 0.581
63 Switzerland 0.575
64 Yugoslavia (1918-1943) 0.575
65 Belgium 0.567
66 Fiji 0.566
67 Saudi Arabia 0.553
68 Bahrain 0.551
69 Iraq 0.549
70 Brazil 0.549
71 Mexico 0.542
72 Macedonia 0.535
73 Pakistan 0.532
74 Israel 0.526
75 Burma 0.522
76 Tajikistan 0.513
77 Estonia 0.511
78 Moldova 0.510
79 Jordan 0.509
80 Panama 0.507
81 Czechoslovakia (1918-1992) 0.505
82 Spain 0.502
83 Chile 0.497
84 Guatemala 0.493
85 United States 0.491
86 Georgia 0.490
87 Uzbekistan 0.485
88 Venezuela 0.483
89 Laos 0.481
90 Morocco 0.479
91 Oman 0.439
92 Thailand 0.431
93 Sri Lanka 0.428
94 Ukraine 0.419
95 Nicaragua 0.402
96 Turkmenistan 0.392
97 Singapore 0.388
98 Dominican Republic 0.387
99 Croatia 0.375
100 Belarus 0.372
101 Zimbabwe 0.366
102 New Zealand 0.363
103 Cyprus 0.359
104 Botswana 0.351
105 Lithuania 0.338
106 Russia 0.333
107 Slovakia 0.332
108 Burundi 0.328
109 United Kingdom 0.324
110 Czech Republic 0.322
111 Algeria 0.320
112 Romania 0.300
113 Turkey 0.299
114 Bulgaria 0.299
115 Swaziland 0.280
116 Taiwan 0.274
117 France 0.272
118 Mongolia 0.272
119 Lesotho 0.255
120 Argentina 0.255
121 Costa Rica 0.238
122 Vietnam 0.233
123 Slovenia 0.231
124 Bangladesh 0.223
125 Uruguay 0.218
126 Cuba 0.213
127 El Salvador 0.198
128 Sweden 0.189
129 Azerbaijan 0.188
130 Hungary 0.186
131 Cambodia 0.186
132 Honduras 0.185
133 Rwanda 0.180
134 Ireland 0.171
135 Jamaica 0.166
136 Egypt 0.164
137 Philippines 0.161
138 China 0.154
139 Libya 0.151
140 Australia 0.149
141 Armenia 0.134
142 Finland 0.132
143 Paraguay 0.132
144 Denmark 0.128
145 Austria 0.126
146 Norway 0.098
147 Albania 0.097
148 Germany 0.095
149 Haiti 0.095
150 Yemen 0.078
151 Netherlands 0.077
152 Greece 0.059
153 Poland 0.047
154 Portugal 0.040
155 Italy 0.040
156 Tunisia 0.039
157 Japan 0.012
158 South Korea 0.004
159 North Korea 0.002
pretty interesting list.